Shakley Products - Scour Off. I think their stuff is all natural and as best I can tell, it works its magic because of a very (VERY) fine grit. I left the spray on my club for MONTHS, thinking it was dry and i could wipe it off anytime. No - it was really stuck on there. Tried windex, finger nail polish remover, etc. No good. This pasty stuff was rubbed on and a minute or so wait - a little elbow grease with a scouring pad - and it is like brand new!!! Did not damage the club face at all and no residue.
I will use the spray again - it is a great learning tool. But I will be sure to wipe it off after each use.
