I torch the handle off with a plasma*, then set it on its side on my welding table. I run a trucker strap over the tank and connect the hooks. Cinch it tight then get on the valve with a pipe wrench. The more stubborn ones need some persuasion with a pipe. Having a heavy welding table helps.
*Not gonna lie, the first few times I used the plasma there was definitely a "pucker factor". I learned this tip from Gus and he's still alive, so....
YMMV