[67_C-30]

Anytime I've ever colorsanded, I have always sanded until all visible orange peel was gone. 3 coats should be enough, unless they were very light coats. Unless you are experienced with the buffer, I'd maybe practice a little on something else. You can burn through clear in a hurry if you're not careful. Be very careful on any body lines, seams and ridges, for example like the raised wheelwell opening in the second pic. It is extremely easy to burn through on places like that. Another problem area is like door handles, antennas, wipers and anything the buffer can catch and dig in around. Be careful around those too.