When I repaired the rust on my sister's jetta I just used a spray can of black paint. It turned out pretty good. Its definitely not perfect, but on a 14 year old car (its a 2002) it blends right in and you can't tell unless you're looking for it. So, IMO you can totally do it. How long it'll last is another question that I don't have an answer to.
Before:
Sanded down:
Bondo and sanding:
Primed and sanded:
Painted:
