Do not try to lap this (or any of your valves which may look like this) without getting them cleaned up first. You must know carbon is a very tough substance (remember what diamonds are made of, right??). Given that, if you tried to start lapping this you will cause some major scoring on both the valve lip and the seat. It will be just plain ugly.
I'd highly suggest you do what Jafromobile showed to do in this video.
For the uninitiated, he suggests you get a brass wire wheel on a grinder, then put masking tape on the stem of the valve, secure the valve stem in a drill, then using both the rotation of the drill and the wire wheel, clean the heck out of them. The dual action of both the valve spinning and the brass wire wheel should do the trick, as well as prevent a single area from getting hammered too much. Here's a still as he works from the side to clean the backside of the valve.
I realize the carbon is going to be a bit tough, but if you want to reuse the valves, you'll have to get these clean before you can lap them and hope they'll seal.