I don't know about the airmaster but the one I have I don't need the moisture coil as the compressor is totally self contained. i don't use the coiled air hose either. That's all you need is to have it "coil" right into your perfectly painted cake (man, I hate when that happens).
As for changing colors, just dump out the leftover from the previous color and rinse the air brush under hot water. Make sure you fill the cup and spray the water through a couple of times till the spray runs clear then put in the next color. Actually doesn't take near as long to do as it does to explain. LOL
I don't know if the airmaster is self contained...is there really alot of moisture to worry about?
The thing is $25 and I don't want to have to get it right away...maybe if I find out I need it, huh?
I'm saving up and I'm almost there so I would love to get it asap. 
I think it depends mainly on the area you live in and how humid it is. Maybe you can determine in the meantime if it's necessary to actually have one. We don't have one on the compressor we have at work and it's been goin strong for like 4 years now.
Occasionally I will clean out the fan filter (it gets pretty yucky with the overspray). Probably the only thing that will need replacing anytime soon would be the needle. If it gets just the little bit bent on the tip you get gloppy's on the cake. It can be straightened out but that is only good for a couple times and then it needs to be replaced. Thankfully they aren't really all that expensive. And yes I did get my setup from sugarcraft too.
Quote by @%username% on %date%
%body%