I like the Aztek Airbrush and have used same for many years without any major problems. I have both the plastic-body version and the metal-body version; both have similar internals that require understanding and a modus operandi that differs from using the conventional type of long-needle airbrush.
Now that the Aztek Airbrush is, according to information received, discontinued in production, a number of these airbrushes are appearing on the secondhand market: buying a used Aztek Airbrush is always a bit of a gamble unless you are able to try out all its functions personally before purchase. Many Aztek Airbrushes have not been managed and cleaned properly, and many have received nothing short of abuse caused by lack of knowledge, understanding, and the use of procedures that do not suit the design of the airbrush at all - like sticking your finger over the nozzle and back-blowing through the cup: you might get away with this on a conventional airbrush but on the Aztek this will cause paint & thinner to be blown past the seal (on the operating rod that controls the nozzle-needle) and into the body of the airbrush itself, thus contaminating those working parts inside the body; witness the secondhand Aztek Airbrush that (provided the trigger is not physically broken) no amount of adjustment can induce it to work double-action, and it resolutely remains single-action; only complete stripping down and cleaning of the body internals will restore the airbrush to function according to its design intention. Stripping down will entail some adventurous working with delicate small parts, and you will soon realize why Aztek Airbrushes require understanding of their internal mechanism, and a modus operandi that respects their unique construction.
As a general rule I never stick my finger over the nozzle of any airbrush and blow back through the cup, I regard this as ill-advised, and no substitute for proper manual cleaning of the airbrush - irrespective of make - immediately after use; on average it only takes about thirty-minutes to strip, clean, dry, and reassemble any of my various makes of airbrush, leaving them ready for immediate use in the future; whereas, faced with a seized internally contaminated airbrush that has not been maintained will cost you hours of delay.
There are nine nozzles available for the Aztek Airbrush (not all boxed sets contain nine nozzles) colour coded for ease of identification, they cover a wise selection of applications, making the Aztek a versatile tool for many people interested in using an airbrush across a wide creative range; the only problem here is that nozzles are put away not cleaned properly; here (below) is an extreme secondhand example:
It took me some time (above) to gently prise the needle out of the nozzle housing; however, once removed gentle brushing with artists' thinners and an old toothbrush cleaned up the needle, and standard airbrush cleaning brushes and tools were used to clean up the housing both internally and externally. A clean example is seen in the image below:
In my experience the needles come out for cleaning and go back into the housing, and the housing back into the colour-coded nozzle, without any difficulty, and this is the only way to tackle congealed internal contamination.
Whilst reassembling I thought to add these two images (above & below) to help those unfamiliar with the workings; this is a well-used A470 example with plenty of commission work behind it: you can see the internal staining of the bodysides caused by seepage past the seal through which the indicated shaft passes: you are always going to get some natural seepage into the body, however slight, as there will always be a tiny amount of back-pressure during use; this is completely different to the back-pressure exerted on the seal by blocking the nozzle with your finger! So every couple of years or so a bit of internal maintenance and cleaning will be needed on this all-important shaft that converts movement on the trigger into the fore and aft movement of the shaft, the tip of which engages into that little (in this case) turquoise cup on the end of the needle spring (upper picture) and thus the needle tip moves in and out of the nozzle to control paint flow; air flow is controlled by vertical movement of the trigger, as in any double-action airbrush; the silver roller wheel on the top-rear (lower picture) of the airbrush allows the selection of single-action or double-action of the airbrush: move the roller to the right for single-action; move the roller to the left to engage double-action; experimentation on the individual airbrush soon establishes how much to adjust the roller.
Eventually, like anything mechanical, parts will wear out; coupled with the discontinuation of production, cannibalization may become the only way to keep these airbrushes working, unless somebody starts machining replacement parts, and supplying plastic replacement hose.
Talking of parts, you may come across a variant whereby the metal linkage fore and aft of the plastic trigger is also made from plastic, and some users have reported failure of this plastic linkage, resulting in a non-working trigger that just flops about in the upper-body slot; the remedy for this would be to fashion, from suitable strong wire, a linkage of the correct dimensions resembling the linkage in the photo (below) and this remedy should not be too difficult to achieve using only the most basic of hand tools.
When looking at these airbrushes from the outside it is difficult to tell whether they have plastic or metal trigger linkage; although, to my eye, the metal linkage triggers do seem to sit a little higher and more upright in the body, and I certainly prefer the action of the metal linkage, as the action is more positive compared to the plastic linkage which feels a tad spongy in operation; I also think adjusting the single-action/double-action roller wheel is more positive with the metal linkage. As far as I can see both versions employ the same moulded trigger, and other internal parts look similar too.
I have enjoyed using the Aztek Airbrush, it has provided me with some excellent results; my approach always being to consider which airbrush in my armoury is the right choice for the job in hand.
Most long-term users of the Aztek Airbrush have developed their own methods for keeping these tools clean and serviceable, and there is much evidence of this on the internet in the form of words and images; there is also a lot of dissent from people who hate the Aztek Airbrush. I think more people would have gained valuable use from the Aztek if they had approached the tool differently, and not tried to treat it like a conventional airbrush.
Similar in principle to driving my wife's manual gearbox vehicle, and driving my own automatic gearbox vehicle, I climb into the driving seat and just switch from one to other as needs be, and I don't find any problem switching from one to the other and back again: I understand how both work and adjust accordingly. So with my airbrush.
I think the single most important word concerning the Aztek Airbrush is delicate, by which I mean handle the tool with respect; don't adopt heavy-handedness as a means to problem-solving; when things go wrong calmly trace the fault by a process of elimination of all possible causes until the fault is found, and then work out a solution to fix it.
All the above applies to out-of-warranty Aztek Airbrushes; if you do still have warranty on the product, and can obtain the services of that warranty, then use the warranty to fix a problem.
Keep it clean out there.