Rubberset 100 restore question.

Hey guys, I got a Rubberset 100 the other day. It was dirty and dull, but it polished up real nice with Mothers. I used strap wrenches to twist it apart and I cut the rotten brush as short as I could. Now here comes the question:
I bored out as much of the old plug as I could, but is there a shortcut to get the rest of it out? Do I just chisel the old epoxy out, or does a trick exist?

Thanks in advance for the help.

I have used a flat bottom cutter in my dremel.Attachment 316561
Take a little at a time so you don't go too deep.

Drill a bunch of holes in it. Then bust it out. :shrug:

Depending on how low you're trying to set a replacement knot, you could just leave that shelf in there.