Cut and polish
There are many Lap combinations for cutting and polishing. This is my way.
Pre-forming
Back In the 70's and 80's when I was cutting sapphires for a living in Rubyvale Qld. the sequence was 260 topper for pre-forming and cutting mains and girdle. Then straight to 1800 diamond on copper, it was quick, no orange peel, no scratches. This method used a bit more diamond and was a bit messy but as long as you didn't let the swarf build up it was well worth it in time saved.
600
If you have problems going straight to 1800 diamond, then go back and cut the table and mains on the 600. Then onto the 1800.
A note on mixing diamond.
I mix the diamond with a small amount of oil, then add CRC. Apply a small amount to the lap then use a piece of paper towel to wipe off the excess. Don't discard the piece of towel, use it again when the lap needs refreshing. This applies to both pre-polish and polish.
Pre-polish
1800 diamond on a copper lap. Most cutters use 3k diamond but this is too slow for me. Pre-polish all the facets, It's also important to pre-polish the girdle, if you don't, particles may break away from the rough girdle edge and cause scratches. Scratches may also be caused by too much swarf or not enough diamond. You won't be able to polish out bad scratches.
Polishing
A good polish depends on the lap you are using and how you use it. Most cutters use 60k or 100k. I get a better polish on copper with 14k than I do with 60k.(more scratches) But can never get rid of the few very fine scratches. I have tried just about every method there is for polishing, but always go back to 14k on an alloy lap, (similar to a Batt lap), excellent polish, fast and facets can be moved.
I have a 20mm section on the outer edge of my laps with 1800. I use this as a touch up area, a real time saver.
