Ok, I did this in college as a prep guy for a foreign used car lot (think Jag, Merc, BMW, Porsche)...
Start with a cold engine
Spray the snot out of it with
start engine, let run for a couple min, and then spray off with hose. (not pressure washer). Let run till dry.
spray down hoses and rubber with
It'll look like it just left the detailers...
and you will be able to spot oil leaks quickly.