paint sanding tips?

i am using value pro base color with clear over it on my project and i cant remember what grit to use when i wet sand just before shooting the color. i spent all last summer building the motor and forgot all about how to paint!!! some guy at the paint store swears that it is supposed to get hit with about 320 grit and no finer than that or the paint wont get much bite. i cant see how i could do that coarse of a grit without getting the scratches to show through the finished product. i was thinking of getting it down as fine as 600 or 800 wet paper, or something like that. any ideas???

Your paint manufacturer should provide a spec or instruction sheet which should include sanding specs. I came up with this site, it may help.
http://yhst-13811118617756.stores.yahoo.net/valupro.html

BTW from what I can recall, 320 is plenty fine for sanding the primer.
600-800 wet is intended more for sanding color coats