In a forum quite a while ago I remember reading about what to use as a cushion for the dial when you soak in in the Clorox solution.
For about two years I used a paper towel folded to fit the container and it worked well. Now I use a piece of the anti slip rubber material, generally used to keep things from sliding around in a Marine application, RV or Motor home. It's kind of a honey combed soft rubber.

You put it on the bottom of the container and set the dial on it while it soaks, correct?

I took the finest little paint brush I have, scissored off all but 3/16 if the bristle. Use to brush those nasty hairlines during soaking to encourage the black stuff to move on.

Another thing to consider, if you have any, is an old porcelain dial turned so that the feet are facing up. I have used it with great success.

Regards,
Larry

Here is a picture of the rubber. Just cut it to fit.

I have found over the years that the little brush works good. I soak it, brush it, and soak it again. Then I use an automotive paste wax over the entire dial. This seems to plug the hairline and also makes the dial shine. If the hairline is full of wax it can''t re fill with dirt.