[Excel_Collision]

you never have to use primer unless you're covering up body work. a light coat of etch primer over bare metal is the only thing you really NEED to do. personally, i'd use Duplicolor engine enamel if i wasn't going to use real automotive paint. obviously tape off the important areas, like the inside, but then prep and paint/clear the entire valve cover, letters and all. put it on the engine once it has dried to the touch (1 hour+). make sure not to get any oil or anything on the VC when installing it. you need to 'bake' the engine enamel, so drive around for a while and make sure the cover gets nice and hot. you want to get it up to temperature and then let it cool for a long time until it's actually cool to the touch. assuming the clear isn't tacky yet (never know with spray can crap lol), you can then tape off the majority of the VC except for the letters. just tape a rough rectangle around the letters and cover the most painted surface that you can (don't go nuts here, just protect it). grab a hard block and some 180 grit sandpaper and start carefully sanding the letters. GO SLOW , go one direction (left/right) on the VC, and don't dig with the paper, keep the block flat. once all the paint is removed, step up the grit until you get the finish you're looking for. you could take it all the way to 2000 grit and polish it if you wanted. carefully remove the tape and you're done.

with that said (and a very basic explanation at that), i'd still recommend using real paint or getting it powder coated, but since money is a concern duplicolor engine enamel should work the best.