I've used brake fluid, freely, without any difficulty. It keeps the stones from clogging, and you can clean it with either alcohol or water. I wouldn't use any petroleum-based solvent for honing brake cylinders because of the trouble with cleaning the petroleum oil out of the system. The stones will wear out eventually, but they will last for quite a few cylinders using brake fluid as the lubricant. You could use water if you want to, but use a lot of it, and wash the cylinder with brake fluid when you are finished. You can't use water if your stones have been wetted with petroleum oil.
Harvester
