I have a Vacu-Tech and have never had problems with leakage. It sounds like in an effort to monkey with the fittings you’ve botched the O-ring seal on the top of the tube. This is the seal that sits within the white plastic fitting. If so (it doesn’t sit even), back off on the fitting and re-sit the ring. If you’ve ruined the O-ring I’d think you could find a replacement at a hardware or auto store, or just give Vacu-Tech a call and have them ship one out. That seal is how the tube and the hose maintain contact, and can’t be fixed with tape or such. You should not have to adjust the vacuum in the tube very often at all, only occasionally as your unit swells.
Vacu-Tech specifically recommends Alboline as a lubricant in the product instructions. Alboline is marketed for removing make-up, and can be found in pharmacies. It is a petroleum-based product that is much less viscous than vaseline and melts on contact with skin. A tub costs about $10 but it will last awhile, and it is ideal for the purpose. Vacu-Tech recommends cleaning after each use, but I no longer do this and I’ve noticed no effects on the tube material. I wouldn’t recommend using water as a lubricant. It has no staying power and this could part of the reason you’re not getting a lasting seal.
Use the Alboline to coat yourself and achieve as much of an erection as possible before going into the tube. That should help with obtaining a good seal to start with.
As for hair removal, shaving in the shower with soap was my technique for years. I’ve now graduated to waxing every week or two, as has the wife. Stubble can be a bitch for both of us. I don’t like going down on a five-o’clock shadow and neither does she. The product we use is bio-wax from IGIA, available on-line. The pain lasts only a second but the smooth lasts a long time.