paint availability depends on where you live
durability is 100% dependent on the materials used and prep done.
Rattle can (from ace, home depot, auto stores) can give a beautiful finish, but it is not as durable as automotive paint (also not as toxic), I really can't make a call on durability of brush on paint, but assume it is less than automotive paint
it also will be more expensive than you think to do a good job I generally suggest people look into powder coating
I did a lot of research a while back on this and have painted 2 frames, one rattle can and one automotive paint
Process is same:
- have a good respirator/filter mask
- Start with frame with notpaint ever or all previous paint removed (removing paint is a pain, lots of time and stripper)
- mask all places you don't want paint
- wipe frame with pre paint cleaner or acetone, handle only with fresh gloves after this
- acid etch primer (assuming steel frame)
- Sandable primer
- Sand
- use tack cloth
- 3 coats color following dry time between coats
- 2 coats clear
let site for month or so before building