I cheat.
I open the sprue plate, put a 1/4-20 nut over the cavity, fill and let solidify. That gives me two castings with a way to turn it. I then open the mold let the castings fall out.
I take the castings, smear some Clover on them lightly, put ONE casting in a cavity, lightly close the mold, and turn as I close it. I do this with both cavities. When the castings spin easily I then either consider it done, or switch castings and spin again.
Piece of cake.
I then toss the castings with nuts in the pot. I recover the nuts when I shut the pot down.
The grit, being corundum floats on the melt.
I cast a few in the mold to clean out the residual grit.
Simple for me. But, effective.
I had a mold I had to clobber with a rawhide mallet each time to get release. Now, I just tap it with my dowel I use for opening the sprue plate.