On bikes in that condition and general "low end" quality a brushed paint job is a good alternative. Get a good quality gloss enamel and a 3/4" art brush. Apply a couple thin coats and you will be amazed at the results. I have had very good results using Benjamin Moore Impervo gloss enamel. Flows on beautifully. I work around the original decals and headbadge. I prepare frames by sanding and wiping down with mineral spirits. Takes about a half hour per coat to paint.