Well, here's what I do ...
I use one of these:
to hold my lockring tool, so I can easily get a lot of leverage.
I usually sit in chair with the non drive side of the wheel facing me.
Lean over the wheel and install the chainwhip (or cog_holding_tool - my preference) so that it's handle is pointing to the left.
Install the lockring removal wrench so that it's pointing to the right.
Now, lean over a little and push down on both "levers". Use your weight.
That pretty much always works for me.
Alternately, another method is to put the lockring tool in a bench vise, sit the wheel on it and turn the wheel in the lockring_loosening direction. This is a pretty standard shop trick and you can even enlist the help of another person.