You can go the exspensive route. Nitro Blast / Spray. You can get this at any hobby shop. At least if they are a real shop theyll have this. It can be exspensive and overtime a big hit on the budget if you demand a highly cleaned car.
I have an air compressor and I use an engine cleaning tool which will suck a solution of simple green and alcohol out of a container and blast it over my car. Much like a nitro spray can, except much higher powered and cheap and not bad for the evironment or my lungs.
Heres is the tool that I use. Got it at harbor freight for 8 dollars. You can find many like it at almost any good tool store that has a good selection of air tools and accessories.
Check it out