I can tell you how I do it and it may help. I pick up the phone call my sister and tell her I am coming out for a couple days. Drive out and shoot all of hers then go to all the neighbors and shoot theirs. Usually before the weekend is over at least one neighbor will come by and ask if I will shoot theirs too. Never run out of targets.

If you want to shoot on private land it really is as simple as finding pds and asking. But I have never shot them in Montana or SoDak so things may be different there.
You may want to check into WY which has more public land than anywhere available for shootin pds.