Whats the best way to remove carbon build up on exhaust and inlet valves when they are removed from the head?

 

I find the best wat to clean them up by using a drill. put the stem of the valve in the chuck (dont tighten too much or you damage the valve) put in the vice an put the trigger lock on this leaves you to use some fine emery tape of some steel wool. then relap them when your building the head back up.