Seems a lot more tedious than my efforts, however I have never had any trouble getting the mount nuts loose - your results may have varied.
Normally I don't jack up the car, just the engine and sometimes I do it one side at a time. That seems to reduce the likelihood of untoward engine motion. I also avoid the use of bricks, much preferring large wooden blocks. (Not jacking up the car reduces the number of blocks you have to use. Also reduces headspace.) BTW I usually use 164/B30 engine mounts. They are sturdier.

You don't have to drop the tranny to replace the rear mount, but you DO have to hold it up.
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George Downs Bartlesville, Oklahoma