A hot car wash also works. I use Castrol degreaser and stiff brush on the cylinders and then hit the car wash, I have one a few blocks away. The hot water really cleans and it gives me one more chance to clean out the water jackets. Take a towel to dry the cylinders and hit them with oil or WD40 ASAP. Flash rust is not all bad, most of it wipes right off.
Joe
