I just used the brass fitting wonder pump style. Two things, one, the best way to "relax the tubing" is stretch it out across to top front of your van cab. Use the sun visors to hold it in place. Ride around alll day like that and the warm temperatures will do the trick. Two, the brass fitting gives alll the extra weight you will need to keep the pump submerged. I just finished pumping Soils and Oils out of my drum, which is 3/4 empty with no problem.
This little pump has my "Honest Cleaner" seal of approval!