I have brushed gloss enamel for years, mostly on my car model interiors because I sprayed the exteriors.
A few tricks I learned along the way -
I use a natural bristle (not nylon or poly), soft, fine hair brush.
I slightly thin the paint (mostly Testors) with a little linseed oil.
That retards the drying time where thinning with paint thinner (mineral
spirits) doesn't.
If I have to apply another coat, I wet sand with 1200 grit or finer.
If the final coat isn't perfectly smooth, but not bad enough to warrant
another coat, I then use either rottenstone or Crest toothpaste to give
it a final color polish/sanding. I have at times used an automotive
"cleaner-wax" applied with cotton swabs (Q-tips) with good results.
A helpful tip - to prevent excess dust build-up settling into the slow
drying paint, I put the items in a small plastic box with a lid
(Tupperware or Rubbermaid) for a couple of days until dry.
Another place to look for deals on AB's & compressors besides Dixie Art -
AirBrush-Depot, they have decent kit prices also.
Sorry for using the names of brands, but that's what I use.