Flax soap.
Sherwin Williams used to sell this to clean hardwood floors. I've no idea where it could be bought today. My dad picked up 9 cans of the stuff on a clearance rack years ago. I've been using one can for over 8 years now. Easy to use. Wet a wash cloth and squeeze out to damp. dip a smidge on your finger and rub into rag. Roll cases on rag and size. A little goes a long way. Have a second damp rag at hand to wipe cases clean after sizing. Leaves brass nice and clean. damp a Qtip with it to lube inside of case mouth.