Here is a non-show related clean up I tried on the engine bay of an 87 firebird. The bay was showing typical surface type scale rust (for the northeast, LOL), but no rot, that was going to take WAY too long to fix (sanding, filler, sanding, spot putty, sanding...sanding...sanding). I didn't need a show quality surface so I cleaned the scale until I just had minor pits. I then applied one of the now common rust converter sprays and waited for the metal to turn black. I taped of the booster, strut caps and anything else I didn't want to get sprayed,like the openings into the fenders. I used a couple of cans of "speckle" paint (or trunk paint) that comes in lots of different base colors with accent pigments mixed in. I chose a blue base but there are blacks and greys and reds, etc. The spatter effect hides ( even "fills" ) the rust pits and I don't have to worry about body filler coming loose. Again, not for show cars, but good for a daily beater that you want to open the hood on occasionally. Hope this helps somebody out there.