I always alternate pumping and clamping in my workouts, starting with the pump, but I do full sessions of each, i.e., not just a brief pump. I always end with the clamps, keeping them on for as long as possible until the engorgement subsides (generally half an hour). I then hang a light weight (2.5lb) to maintain elongation. Have to use an ankle weight as I, too, cannot get PEWeights on.
I feel that the pumping, while it has its own benefits, also gets the tunica stretched to a level where the clamping can take over. Then, pumping again after clamping builds on the stretching done by the clamping. All speculation, of course. But I remain huge for quite a long time afterwards, which I feel is a good indication.