Open the valve to relieve any pressure. Secure the tank the best you can. Inserting a pipe through the handles is a good way. Then use a crescent wrench with it just opened enough to be inserted in the hose opening, so one jaw is on the inside and one jaw is on the outside. You are basically using the crescent wrench jaws to bite on the edge of the opening. You may have to turn the wrench over to get the right bite. Then using the pipe to hold the tank in place either flipping it on it's side or having a second person hold it, un-screw the valve. They are usually in pretty tight, so using a pipe (cheater) on the wrench will probably be needed.
There are other ways, but this is the easiest.
David Reiss - NRA Life Member & PSC Range Member Retired Police Firearms Instructor/Armorer
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