There are only two things that should be used to clean the hydraulic parts of a braking system one is brake fluid and the other is a combination of soap and water. If you go the soap and water direction you will need to make sure all pieces are water free before re-assembly.There are special types of lubricant that may help with re-assembly.Brake/contact cleaner should never be used on any hydraulic parts of the brake system, they are good for cleaning pads, shoes, discs, and drums.