RE: How do you cover the engine cowl?
You can paint with Krylon, but you should then apply a clear fuel proof paint.
Luster coat ( the line form Monokote) is mixed to match their line of covering (Monokote) and is fuel proof. They also sell a clear spray, to 'fuel proof' painted surfaces and decals.
PPG paint, which is typically 'car paint / autobody paint' is also fuel proof..