i used rustoleum and it looks great. I have not driven my truck as of yet so i will find out (hopefully soon) how well it holds up. Fairly inexpensive and i brushed it on with a paint brush. If you look at the pictures, you can't tell it was brushed.
1. Cleaned, major spots with wire brush, vinegar water, rinse with water
2. Rusty metal primer
3. Rustoleum marine based paint (i used semi gloss paint)