I've used the purple industrial cleaner at Home Depot. I sprayed it on with a $12.00 siphon "sand blasting " gun also from there. I sprayed it straight from the bottle, hit it with a nylon brush after waiting about 5 min. then rinsed with a garden hose. It got the better part of the 46 year old grease and dirt off the first time. It did take some of the "Newer" rustoleum paint that my brothers put on in '96. It didn't touch the original paint though. I've done the engine, trans, frame so far and sure beats the wire brush. Just rinse well and use a compressor to air dry if you don't want it to rust in a day!
