I've got some 220, 400 and 600 grit sandpaper that I'm using to finish aluminum.
I've started experimenting and noticed quite a bit of different when I sand with versus against the grain. Is there a "best practice" for this?

Also, I've never used "wet" sandpaper before. Is that a must-have for this process? I'm not looking for a mirror-finish; simply trying to get rid of endmill tool path marks.

Thanks!