X2 on purple cleaner. I buy it by the gallons. Get a good spray bottle, get it wet, spray liberally with purple. Let sit and rinse, repeat and use a scrub brush on the stubborn areas. I have a cheap parts washer from harbor freight ( was under $40 with a coupon). Its a plastic tub one with basically a small pond pump. You can't use harsh stuff in it because it will eat the pump. It's small enough to use when you are wanting to do a good cleaning on say your brakes when you do pads and whatnot too. When done I pump it out into a jug or two for the next time.