I just use whatever I am using on the rest of the car. This is with a PC though. It might be different with a rotary because the heat might do some damage to the plastic lenses. I'll let someone else chime in on that.
On plastic I use scratch-x and polish by hand. A UDM/PC type works as well. But by hand does fine I've noticed if your doing it after the fact. Don't be scared to polish them with your metal if your doing an all over polish.
I have had good success with Meguiar's Plasti-X. You have to rub pretty hard by hand to get sufficient results and a couple coats may be needed, but it should improve clarity by at least 90-95%.
Same her, I just take it a little easy with the rotary (no such worries with the PC/Cyclo). I wouldn't get *too* aggressive though, some such materials don't respond well to serious correction; tail lights seem to loose UV resistance if you over-correct them and some (few) headlights have, IIRC, something in their outer layers that ought not be removed through aggressive abrasion.