Work in progress. Add pics and more instructions
Use a large square glass plate. Put a small scoop of 600 grit powder (same as is used for the abrasive drum in the LP50) on the glass plate. Add water onto the plate and the power with your hand or a squeeze bottle of DI water. Gloves preferred. The thin section has already been cut and ground down on the PetroThin. Place the thin section face down on the glass plate and rub around in small circles in the slurry. Be sure to go back and forth in different directions, and change where your fingers are pushing down, to get an even thinning. How hard you press is dependent on the material, hard can take a lot of pressure, softer you have to be more careful. If you feel something scratch the thin section stop. and wipe the slurry away with a paper towel where you think the grain/dirt/whatever was. Add more water as you wish to keep slurry liquid and smooth. Samples may need only 1-2 minutes, or 5-10 minutes of this hand lapping. Get it down to around (50 microns???) in thickness and move on to the next grit.
Wash the thin section off in water to completely remove all grit, clean with isoprpyl and kim wipe.
Use a different glass plate and repeat above process with 1000 grit. Get it to 40 or 30 microns thick with the 1000 grit. Now it's ready for the PM5 polisher.
Even when using the LP50 to lap, I strongly recommend hand lapping at least briefly with the 1000 grit before putting on the polisher. It gets a much better more effective polish.