I have a kit from Wheeler that comes with 600grit lapping compound. It comes with alignment 1" pieces that helps you to align dovetail rings. Then you can start lapping. You put the compound on a 1" (or 30mm) steel rod and mount like you would a scope. You then work the rod back and forth to remove/hone the inside of the rings. Now they should be more or less more round than before. It removes and burrs from the inside of the rings also and gives a more positive contact for the rings to scope.

I like it cause I hate scope rings with inserts. I can never keep them zero'd on hard recoiling guns. So I like leupold steel rings. But they sometimes leave ring marks on your scopes. And I trade and sale alot and don't like that.

They claim also it keeps the scope more aligned so its not "torqued" which they say can cause POI changes, scope damage, etc.