hey , check this thread out..
http://nissancustoms.com/showthread.php?t=8110
its a how to on shaving ... missing few steps , but basicly to give ya an idea....
alot of shops/people do it differently . so this is not law.... but should always be best to get the metal straight as possible before , bodyfilling ... and weld it solid with tacs..... if you do it like that... then theres no need to use kittyhair or any fiberglass fillers.. just skim some Rage gold over it and sand and primer....