best way to clean a....

well, im working on the uderside of the van and it crossed my mind to clean everything possible.
i had tried this before but due to the time i had it was not clean as i would of have like it to.
what have you guys used to clean the trans?
chemicals? degreasers? pressure washers? any info is welcomed.
also what kind of paint to use, if any


thanks

I would use a good under coating like the spray on bed liners. You can apply it with a brush. I will be using Eastwoods coating

Brake cleaner

One of the guys on Moparts swears by a real steam cleaner, not just a pressure washer. It will even remove a lot of the undercoating.
For large area hand use, it's hard to beat the combo of a good degreaser (example; simple green) and various brushes. Consider the brushes disposable. For metal components like a transmission housing, brake cleaner is good, but try to avoid painted surfaces and your own person!

At some point in time a p.o. sprayed that horrible undercoating that never dries under my 68 pickup. Fast forward to my ownership. I jacked up the truck removed wheels and put on blocks. Truck sat about 3' off the ground. I used a hand pump sprayer filled with kerosine. Applyed let sit for 24 hrs power washed and then applyed again. Let sit for 24hrs went under truck armed with putty knifes and wire brushes and cleaned all the heavy deposits. Sprayed with kerosine again. Let sit another 24. Power washed again. Sprayed white wall cleaner on everything real heavy. ( This cuts the oils in everything and will let the paint adheir to the chassie.)Power washed and let dry. I painted my chassies with rustolium gloss black. Mix 50/50 with laquor thinner. I Just replaced the floors in my 1969 IH 1300 car carrier. I used the Hercurliner bed liner stuff. (Friend of mine has a spray gun to spray it on no roller.) I sprayed the inside of the cab and underneith. Its a work truck, It came out great! We will see how it holds up with time! It should work well as a sound deadner as well.