Originally Posted by truckernix
I use two hunks of heater hose and two tubeless tire valve stems. I secure it all with gear clamps. I pump a little pressure in, check it with a tire gauge and then immerse the core in water.

Thanks for the description.

Also, I had never seen the term "gear clamp" (I see "hose connections" in the USA Shop Manual) but it makes sense (and, is used in Google Images).