I started pumping, I’m a big-time DIY person, by using an empty tube of caulk. I had remembered a clear type of latex caulk but…couldn’t find one, about $5 for a full one. So I used what I had. The problem is that the tube is opaque, can’t see through it, so a vacuum gauge is vital to this process. It will keep you informed of too-high vac level while in the tube.
I (gently now) heated the leading edge on the kitchen stove by just waving it over the rising heat and determined its pliancy by tactile engagement. Sorry, its the tech writer in me. Just feel the effing thing, when it moves easily, work the movement around until you’ve bell-mouthed the end. Then flatten it in the sink while running water over it. That will give you a uniform seal surface. Don’t push too hard or it will buckle leaving you with wrinkles on the tube. No problem structurally but will look like a bad job. If it doesn’t work to your satisfaction, it can be redone, except for the buckling and even that can be smoothed somewhat. Yep, I did it too.
The plastic is ready to move when it moves easily (funny, that), if it smokes or drips? Oops - too hot! Too cool yet, it’ll be stiff and not want to change shape. Btw, it seems to have a little bit of shape memory so if reheated, It’ll go back to a cylinder, but somewhat deformed.
Length of the tubes are around 10” and they will accept a 1.875 Dia unit (about 5 3/4” EG)
You’ll need a large-to-small tube adapter for your hose.
Hope this helps.