I can't speak for the OP, but I definitely used Grease & Wax Remover then a rinse/wipe (think it was brake cleaner).
Yes, surface prep is usually the most common cause of paint failure, but I knew that and followed directions whistling
I suspect the machine shop sprayed some kind of gray coating or paint on the block to keep it from rusting. Where the paint has come off in big sheets, there is hardly a trace of rust underneath. Maybe I should have sanded first! shruggy