Ok! So I considered all the options I have and what suggestions I’ve gotten, and I pumped today with my hercules pump with NO WATER. I also went in with a cock ring on to maintain the erection, and “jiggled” around the tube up and down like masturbating while in the tube, and I definitely was hard in the tube and stayed hard, so I pumped for around 10 minutes. At the end of the session, I had increased hardness.
When using it without air, and no vacu vin mod, it’s all I can do to just get 2 pumps, and it will not expel any air after that, so the allowed pressure in air pumping with the bathmate is much less and controllable, however enough to create a seal. I will try out this method for a while and report back if I am making longterm progress.