You're supposed to just let the weight of the machine do the work which is easy when working downwards, but not so when working on the side! You soon get used to it, although I did have to keep stopping myself when I realised I was applying too much pressure at various points. That's the beauty of the DA though, as you can get away with making small errors like that.
If you mark up the backing plate with one think black line you can monitor the speed of the pad easily. With a DA it's not always easy to see how fast it's spinning.
Show us your truck Dan!