I don't know how well it works either. I know of people who have done engine compartments with Wal Mart (97 cent cans) paint and they prepped the compartment and sanded it like they would a regular auto paint job and it held up for a long time believe it or not.
As far as the spray can stuff I don't know. SEM and such places make paints for interior and engine compartments and it seems to be pretty good. I'd like to know this one myself.