Get a couple of cans of good spray brake cleaner, I buy and use Wal Mart brand brake cleaner and carb. cleaners for my shop use Spray the block off several times really well with the brake cleaner, then use a good heat gun and dry the block, or whatever other cast iron your going to paint with the heat gun, hold the heat on the cast iron in one spot until you see the moisture come to the surface and then evaporate, work your way over all the surfaces you want to paint twice drrying them out, it will take less time to redry the block on the second go around , and then shoot the paint to it Let us know your results, if you do it this way