OP. You might want to look into some chemical paint stripper, which should speed things up considerably. Check the paint dept at Home Depot. The paint stripper is brushed or sprayed on, let it soak for a while and all of the paint turns into a gooey nasty mess. Wire brush/scrape/sand the gooey nasty mess off. Then rinse the bike off with either water or mineral spirits (depending on the type of stripper). Abrading an entire bike with sand paper and brushes to remove the paint is a nightmare from hell.

Or, take it to a metal-finisher or autobody shop and have them sandblast it.