So. I have a Paasche airbrush i don't use on my minis. I got it for WWII armor and the like. However... I have seen some people using airbrushes on demo video so I thought I would use it my next block of saurus for the first coat (I prime then base with a very light blue green not GW color but more blue green. It is almost white then I do washes. I like the highlights better that way. Anyway I was liking how the coat went, I was experimenting to see if I could get away without primer but alas, I don't think so. We'll see when they dry. But I am happy with that. I just never bothered because I was thinking that minis are so small (well most of them) and why bother with the rigamarole of getting the AB set up then having to clean it and ugh. So that being said, I have not used it for awhile and I can't get the tip out (<---- now come on no juvenile giggling ) anyone have a trick for a stuck tip? seriously though.
Not really sure of all the parts of an airbrush.. What is holding it in place? You could grip it with a pair of pliers and use more force? If it is paint holding it in place, some kind of solvent would probably help like methylated spirits or isopropyl alcohol.
I took the cover off it should just fall out but it is soft metal and sometimes they can "stick" there.
try soaking it overnight in paint thinner. I base coat my minis with an airbrush and it saves tons of time getting them to a minimum standard. Still do the details with a brush.