Mask off all the mating surfaces and the inside of the covers. That would include the oil filter cavity, the back of the oil filter cover and the oil level window. There are oil passages inside the covers you don't want clogged with either blasting media or powder coating. Don't leave the round inspection cover in or you'll never get it out. In fact, you might consider leaving it uncoated since the powder coating will make the slot narrower, and when you try to tighten or loosen it, you'll chip the powder coating.

Also, while your covers are being done, get yourself some washers for the cover bolts. Even though the bolts have flanged heads, they will gouge up the powder coating when you tighten them.

Oh, and if your powder coating guy is good, he'll put tiny plugs in all your bolt holes so you won't need to open them back up.

Thanks for the advice. Where do i get the rubberized washers needed?