I paint the engine bolts seperately myself,I use a very thin coat of paint on them before assembly,and then I put another thicker coat on them when I touch-up the rest of the engine paint after assembly.
Sometimes certain bolts can be a PITA to get covered evenly when the engine is all assembled.
IMO it's easier to just touch them up than to paint them on the engine.
BP.
__________________
This space for rent...
In the meantime,check out the cars
HERE.