I had pretty good luck with Por-15 and their chassis black paint and brushing it on with 25c foam brushes from Osh.
Before:
After:
Just did my interior floors as well:
(Before shot)
Also painted my trans and rear end the same way:
Engine block:
Trunk is next at some point.
For the do it yourself guy w/o access to a good air system and spray gun, Por-15 is a nice alternative (can also be sprayed).
One thing thou prep is key and killer don't bother if you aren't going to follow the directions to the letter and make sure everything is perfectly clean. The slightest grease and it will peel off in sheets. Nice thing thou when done right its bullet proof similar to powder coat. Solvents and hammering on it won't phase it.
Another option might be Eastwood's Rust Encapsulator and Extreme Chassis Black in aerosol had good luck with small parts done up that way.