I am as frugal as you are and I have wrestled with this problem for years. Here is some advice:

First of all paint is a problem. About the only color paint available is butyrate Dope, and that usually has to be mail ordered. Dope is also somewhat expensive at $4.00 for 4 oz. And it takes at least 5 coats to cover, especailly the lighter colors. A 4 oz jar will paint a small model .15 to .25 size. Dope is also not glossy unless you really put some effort into it.

Some guys are using Latex paint but I don't think it is GLOW fuel proof. Some colors and formulations of Rustoleum are fuel proof but be careful!

Personally I use Dope and most often Hobbypoxy. Hobbypoxy or Superpoxy is hard to find but well worth the effort. It hasn't been made in several years. Just a little goes a very long way!!! And it is very glossy. To paint one coat of paint on a .40 sized ship (and it usually only takes 1 coat) you would use about 1 oz of paint mixed with 1 oz of hardener and 1 oz of thinner. 8 oz in a can by the way!

I use a Pashe airbrush and a small automotive "detail" type gun with a compressor I bought new for $100.00 from harbor freight. I have to use 2 different water separators to get all of the water out of the air which is also a big problem.

I think the Wagner is designed to shoot housepaint (Latex) so you may find it difficult to fashion a water separator. Also Latex is much thicker. The Wagner may be designed for much thicker paint. Normally I thin to a water or milk like consistency.

I cover with silkspan, Sig Koveral and nitrate dope all very cheap!

So sell all of the monokote forget the wrinkles and sags and join the ranks of the few who paint!

Let us know how it all works!