When you are painting panels, do you mask off the entire bike? It seems like a ton of tape and takes a good deal of time. When i did my frame I used masking tape for the edge and cut a plastic bag into strips for the rest of the bike, but ended up getting overspray in some gaps. Luckily the panel was white and I was painting over with brown.

Or do you just paint the panel without masking, mask off the panel, and paint the main color over the overspray?

During a full refinish I always spray the panels (or secondary color) first, then mask it off and spray the primary color. When painting stripes on cars, we'd do the same thing, spray the stripe color, mask, then spray the body color, unmask the stripes and spray the whole vehicle in clear. This is where a drying oven comes in handy.