I'm using an advanced technique: cutting out pieces of paper and putting them under the tool while pressing to avoid certain areas of the tool touching the mirror. I know I have a hole in the middle, so by blocking the middle from wearing down I can concentrate my wearing on the outer zones without making the center even deeper.

Looks like after a few hours I've managed to get the outer zone almost completely spherical! There's a bit of TDE left to fight and the center is a bit messed up but I think I'm very close.

From here I could either get everything to a sphere and grind out that TDE and then wear down the center again to make a parabola, or see if I can go to a parabola from where I am now. I don't quite know how to decide.