I use what ever is needed. A lettering quill for details, an airbrush for fades & details and a detail spray gun for larger areas, primers & clear coats. I have also used sponges, leaves and even shot a wad of paper towel out of a tube for a blasted effect. Have also used an old paint brushto get a woodgrain effect.
But as far as painting the whole bike with a paintbrush? You're kidding, right?
Might do that to keep some one from STEALING IT!!

Used to use laquer until I found out how worthless it is on a bicycle. switched to automotive type paints and never used laquer again.

Search down the Classic & Vintage threads for other posts about painting. Most have some helpful info.