I've always had the best luck with the engine running i spray off any serious clumps and wet everything, except the intake obviously. Then I coat everything in simple green, greased lightning, or whatever degreaser let it sit for a minute or two and spray it off. Scrubbing bubbles works extremely well too. Repeat as many times as necessary. I've never had a single problem. I usually let it run for a few minutes afterwards and go for a quick spin to help it dry out.
In my early years I did it with the engine off and occasionally encountered a no start condition when I tried to fire it back up.