For the most part, I finish my models with fiberglass and resin.
Then I paint with good old latex house paint that I have custom-
mixed at the local ACE hardware store. 'Glassing is a lot more
work, (sanding), than covering with film. I have painted over film
covering, usually monocote, with decent results. The reason I
have gone away from covering with film is the fact that it almost
always starts to lift in places that fuel gets under, and fuel will
find its way under everything! Also, you get into the wrinkling of
plastic films. If you do cover with film and paint, use clear or a
light color film like grey or white. Depending on the size of the
model, I use everything from a airbrush to a full-size automotive
spray gun. My medium touch up automotive spray gun gets to do
most of the painting on my .60 size and up models.