Yeah Ben, I just use an old crappy blade screwdriver, and use the corners, the flat the tip, whatever, to make a random pattern, it will not work so great on a large area, but the smaller chunks that come off, it works well.
I hear you about the tennon and jamb chucks, use a donut chuck and a spacer between the inside of the bowl and the back of the donut chuck, I find various sizes of PVC pipe work well, cut to about 2" to 4" long, and then a foam pad of some sort.
Here is the last NE I made, Mesquite and I lost some chunks, but used the burn method to hide my mistakes....
The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
William Arthur Ward