cleaning/shampooing question

[Bugs]

ive got a 1500cc engine, sitting in my garage, waiting for my car to come back from the paint shop. Now this engine is nothing special, but its all i got for now, and will get me past this summer.

I need to clean up 30 years of grime etc. And Was looking at some of the engine degreasers, etc. The one i picked up, is a spray on, let sit, rinse off (and repeat with scrubbing on the hard to clean stuff)

What precautions do i need to do i need to take to not kill my engine while rinsing etc?

Plug the carb to keep water out is obvious one, but what else should i do to keep from damaging things?