Yep, do your sanding and buffing before you put them on. They will take some abuse when polishing, but not much, one swipe on them with sandpaper will permanently damage them. If there clearcoated, there fine to buff if you dont sand thru the edges. It will take an extra few coats to bury them.
Everyone has their own way to color sand. If I do an expensive job, I use 1000 paper. I tear a sheet in half, then fold that half into thirds to make it fairly rigid. You can use a lightly running hose or a plastic bucket of water to keep the surface wet and constantly rinse the paper. Dont make any difference about direction you sand. I finish off dark colors with 1500. On production stuff, i use special sanding disks on my DA sander , 1200 grit and dry. I like this because its very fast and doing it dry lets you see what your doing as you go. Wet, you have to constantly wipe and dry to follow progress. Either way, do very little sanding on peaks and edges...buffer will take care of those just fine.
[This message has been edited by rogergarrison (edited 07-17-2008).]