Lew - I've also been quite pleased with my Harbor Freight dual-action polisher! I changed its backing plate to 5" for the rayon glass polishing discs I linked above. I've found a range of very economic supplies, like backing plates, polishing pads on eBay. (I've also have made some modifications to my unit, like putting on a 20'-long power cord, fixing/optimizing the clearances of transmission gears, and changing the grease.) I've tried harbor freight's
newer model dual action polisher, which has a smaller diameter motor that runs at a higher motor RPM, and didn't like it as much as the older, quieter, more sturdily-constructed unit.
I took a photo this morning of the partly-polished windshield in the rain, which shows the hydrophilic quality of the clean, polished surface (on the left) versus the more hydrophobic surface with old Aquapel treatment (on the right).