This ought to help:
Well you'll want to roll up the tube in a heating pad and let it heat up before you pump. Take it out and let it cool off to a comfortable, warm temp before you start. Lather your cock and the inch or two around it, get a semi, and enter the tube. Hold it tight against your body until you form a good seal, then you can let go. Keep the tube warm by periodicly wrapping it in the heating pad. Never pump much above the first black mark on the gauge (5 inches of Mercury), you are using a gauge right?
If you feel tingling in your head... that is bad, it means that a water blister may be forming, back off of the pressure and shake the tube until the tingling goes away. If you take your cock out of the tube and you notice that you have a tiny bubble forming on your head, you have a blister and need to apply cold (ice) to the blister pronto. Be very fucking careful with the water blister thing...
Shake the tube and kind of lightly jack it back and forth after about 20 minutes or so of pumping. At the 30 minute mark. Take it out and shake it a bit and let it rest for a few minutes, no more than five. Re-lube it and put it back in the tube that you have been keeping warm with the heating pad (not too hot). Pump that sucker until you pack the sides all the way around, you'll need a hand mirror to see this. After you have packed it, leave it in for a few more minutes while reducing the pressure a bit. Then take it off, pee, clean all of the lube off of your cock (really just the base and balls) and put the leather strap that you MUST buy. Here is the link:
Sensual Universe Warning Page
All in all... be safe!!!!