Best way is paint everything in pieces, then reassemble. Like the others said, tape off edges, cover fenders and panels. I picked up ( 3 ) old comforters at the Goodwill store that worked well. If you have lots of help when assembling stuff it should go a lot easier / chance of damage a lot lower. If you are planning on using fender welting, its much easier tp preglue it onto the fender flanges before bolting them up to the body.
