Here's what I do.
1) remove all electronics
2) spray the car down with electric motor spray or nitro cleaner from the LHS. Scrub well with paint brush to remove any leaky oils or grease.
3) spray down with 50/50 mix of simple green and water. scrub well with paint brush to remove dirt.
4) hose car with fresh water.
5) blow off car with compress air until 100% dry.
6) spray the whole car with Maxima SC1 plastic renewer/polish let it set on the car for 10 minutes minimum.
7) blow off maxima SC1 plastic polish with compressed air and wipe off the remaining with a dry towel.
The car will look like new and smell like bubble gum from the SC1 polish every time!