You want the speed of the PC and your product/pad to do the work. A good rule-of-thumb that Scottwax has mentioned here before is to apply just enough pressure to bog the PC down a bit, and then let up until it just gets back to speed.
Iâ€â„¢ll occasionally bear down a little harder for brief periods, but if you have to do it consistently then you need to work a smaller area a bit slower with more than one application or bump up to a more aggressive polish and/or pad.