Dooey do you have a lapping plate you could use wrapped in lower grit paper?
I use wet & dry on my glass plate I use for lapping for thinning most scale materials.
you could go as low as 80 grit paper to rough them thin, then go to the 180 which is i used for bone & was fairly quick (for 1 set) to get them to 2mm from about 4mm
how did you go dry grinding the bone stinks the place out nice hey