I usually take most of my machines to TPF each year... it's become a "religion" for me to replace the balls with new ones as I wax the PFs (clean the titans) for TPF each year. That way every machine I have has fresh balls for the abuse they'll receive at TPF.
I tend to wipe my new pinballs with a rag before I put them in the machine; nothing else is really done at that point since the PF has already been waxed.