I don't know of any guitar finishing forums, per se. Most building forums will necessarily have at least some discussion of it, but in my experience it's tough to get anyone responsible to commit on a particular procedure, and more often than not when you do get advice you also get the impression it's the blind leading the blind. There's usually more than one way to do something, and different people get different results even when supposedly doing the same thing. You sorta have to be part chemist, part mechanic, and part artist with plenty of experience all around.
All that said, here's how I'd do what you want to do. Once the thing has been stained, sealed and fIlled to your satisfaction, I'd shoot the thing with several coats of sanding sealer, then mask your line while also covering anything else you don't want to get any overspray on. You want to use a masking tape designed for fine lines, as the color coat is going to be pretty thin stuff and it'll get under generic or household masking tape. That green stuff from 3M seems to work pretty well, but it's not always as pliable as you need for some curves. You may want to find a well-stocked automotive supply store and get some vinyl pinstripe masking tape.
Then, shoot another coat of sanding sealer over that, which will seal the edge where the tape meets the body. Give it an hour or so, and shoot the color. Don't wait forever to remove the masking; about an hour is probably right. Any faster the paint may move, any longer and it may chip. Then, start with the clear coats. After about 3 or them, you can start levelling between coats. After about 10-12, you can hang it someplace to cure for a couple weeks.
ccasion14: thread and not a :dontknow: one.
