the good old double pot method! i did this for one grow. every single time that i went to move the pots for watering or whatever, i'd grab the top pot and pull or twist. feeling the roots rip would make me cringe. so basically every time i had to move the pots at least one of them got damaged. i would tell myself that next time i wouldn't be so stupid, but of course....Best way to transplant a larger plant is to leave it in the original pot and cut out just the bottom of the pot.
You can then set the bottomless pot on top of the dirt in a larger pot. I do that routinely with those plants
I want to re-grow.
BigSteve.