airbrushing fine detail

Ok I'm a new airbrusher so bear with my stupidity..

I have been playing with my single action Paasche and attempted to paint a simple camo paint job on a 1/35 scale Hummer.
I am having a very hard time getting the paint stream both fine enough to paint a small, precise line and still keep paint flowing thru the nozzle.
Let me make that a little clearer.
My brush came with a no.1, no.3 and a no.5 tip sets. I have tried all 3 and have had the best luck with the largest.
I am using Tamiya Acyrlics and I have tried them both thicker and thinner.
When they are thick you must increase the air pressure and turn up the needle.
When I thin them down I do not get any coverage. Trying to spray Olive drab over tan would take so many coats that holding a reasonably nice edge is not do-able. As you would have to pass over the area so many times you would overspray the edge.
So I have a few simple questions.

First....
Which tip size is correct for Tamiya Flat Acrylics? 1,3 or 5?

What air pressure would you suggest for doing fine camo type painting?

Is a single action brush going to be able to do what I want it to?

Do most people mask camo patterns? If so what methods are most common?

Any suggestions are greatly appreciated. It is hard to learn something like this without someone to watch do it.

I read the post, and you didn't mention if you were using enamels or acrylics. The mention of the thinner used implies enamels, but I wasn't certain.

Jeff
Paasche-H:http://groups.google.com/groups? q=greg+williams,+fine+lines&hl=en& lr=&ie=UTF-8&selm=7910e83b.0302272012.24ebc519% 40posting.google.com&rnum=1

Depends on how much you thinned the paint.
But if you want to spray fine lines, elementary logic screams for tip
#1.
You might also try adding some acrylic retardant to the paint to prevent it from drying too fast.

Depends on how much you thinned the paint.
BUT... to get a fine line, you have to spray at a close distance and a low pressure will help avoid paint streaks.

If you want a sharp edge, place the masks directly on the model or, if you want a slightly fuzzy edge, glue them with blutack, ar anything else that is about 1-2mm thick, so that the edges of the mask do not come in contact with the model. Then spray paint from about 10-15cm.

Practice, practice, practice.
Put your model aside for a while, get some plastic bottles, white paper or whatever and practice airbrushing small dots, fine lines, tiny dots, even finer lines. Again and again and again.