What kind of blasting, bead, sand? I always mask all the gasket surfaces, plug any exposed tapped holes and never blast the inside of the cases or other internal surface that won't get painted. But that's just me. When you get everything back you have to super clean it especially the holes. Best if you can get an air nozzle right into the hold. And once you think you have everything clean you do it again. I take everything to the car wash and use the pressure washer (actually before and after). The less grease is on it the better the blasting will come out and there are less places that grit can stick to. Make sure you do all the oil galleries too. All it takes is one little grit and it doesn't matter how good the paint looks. Good luck.
