I'm a millwright and use my hands often in my trade, I'm no wussy by any means, however there is always a time when I need assistance opening one of my tanks, so I bought a flat piece of rubber that's perforated made just for the purpose of opening stubborn bottles, jars etc.
I'm sure they are in most grocery stores, wall mart, ASDA etc. they've saved me several headaches. Sorry I don't have a pic or link handy.
this was suggested in another thread awhile back, sure glad I picked one up.
Best of luck......
I had this problem too.
I was looking around to see what I could use and saw the egg poaching ring made of silicone that you crack the eggs in to in the frying pan to keep them a small round shape.
Gripped the tank like a dream and opened it easily