I think there is a "tool" for that.


https://www.bikeride.com/bottom-bracket/

I think often if the lock ring is removed, the bottom bracket can be easily removed. But, if not, what I usually would do is take a large adjustable wrench (I have some big ones), and put it on it. Then I'll build up a few washers so that I can tighten my wrench down onto the bottom bracket and hold it in place with the bottom bracket bolt/nut so it won't slip.