Hi Pat,
I have done a little of this, so I’m happy to share my experiences.
I would not use polyester resin in this case. How you mix polyester resin (with hardener) depends on the depth of the casting. I’m afraid it would be rather tedious to get the amount of catalyst just right to allow your resin to cure. Your logic makes sense though, since polyester resin does well on a buffing and polishing wheel.
In this case, I think a hard curing epoxy resin, like the Resin Obsession super clear resin would work well. You can buy it in several sizes in our store here: https://shop.resinobsession.com/collections/resin/resin-obsession-super-clear-resin I have used it in cases like this and did well on a polishing wheel. The resin probably works best once the stone has been polished. That will mean there is less total heat/friction applied to the stone.