I've used a traditional DA, a Flex 3401 DA, and a rotary to jewel with using 85rd (using either a crimson HT, or black pad w/da, and a blue pad w/ rotary). IMO the rotary produces better results. But you can get good results with a DA. With any polisher, be sure to work the polish (a lot) till it is fully broken down. As soon as the polish starts to go clear, reduce the pressure. Continue working it. Once the polish has gone clear reduce the pressure significantly. Make a few final slow passes over the clear polish to bring out the gloss. At this point there is only VERY light polishing action left in the polish it is ultra fine, but it is still refining the surface ever so microscopically. Here is where I believe the extreme gloss comes from. Then I typically make a couple more slow passes with little pressure, to almost no pressure (when using a da you still need to apply some pressure, because of the erratic movement of the spindle). When using a PCxp I run it at full throttle the entire time. When using the 3401 I typically start out at around 5, and turn it down to 4 for the last few passes.
Using a rotary I typically break the polish down in 3 steps:
Stage 1 (1200-1400 rpms) - Firm pressure
Stage 2 (1000-1200 rpms)- Less pressure
Stage 3 (800-1000 rpms) - VERY Light pressure