Leveling isn't that hard, but I've never heard of using steel wool to do it. Pretty much straight from the chapter on Fretwork in Jim Donahue's book "First, take a black marker and mark the top of each fret. Take a block of wood wrapped in 180 grit (although I'd use a milder grade), with the neck off and the truss rod adjusted so the neck is perfectly straight, use the sand block and run it over the fretboard in long strokes from 1st to last. When all the frets have lost the black marker you're ready to move on to a milder paper like 400 to remove the scratches from the courser paper. Next (after masking off the board, best done to begin with) take a broomstick handle wrapped in welting (very think felt) and the same 400/600 and run it up and down the board to put a crown back on the frets and further remove scratching."