Here's Opuntia pailana (hight 65 cm) and Echinopsis peruviana (hight 150 cm). Their plastic pots have broken rims from moving their heavy pots now and then. Not very nice to look at, so I'd like to re-pot them in traditional terracotta pots. Easier said than done ! I suspect that the plants might easily breake. If 'specialist cactus repotters' exists I don't know them. Maybe you have a brilliant method for doing the re-potting without risk of breakes ? Or is it simply too risky and I've better give it up ?

You need a second person, one needs to lift the plant, the other to do the re-potting.
Wrap the stem in cardboard and newspapers, tie it with some sturdier string(like nylon for net sacks) .
Before potting lay the plant on the ground and try to pry it off slowly.
If the pot is ceramic, well, youll either struggle a lot, potentially damage the plant, or break the pot...

I would wrap the Echinopsis with towels and then have someone help you hold the stem and lay it on the ground and then remove the pot. If youre not attached to the pot, its easy to get off by just breaking the pot.

The opuntia, if it was me you have a few leaves that droop down those I would prune off which will make repotting it and stabilizing it easier during the whole process and its basically the same process as the above. You can then just propagate those that you cut off.

It's definitely not hard enough that its impossible you just have to be careful, and cautiously expect it to not go as planned. You got this, you can do it!!

Thanks for the advices. Risky business, so I'm still considering ...

You have been given some great advice. When I did our 7 footer I wrapped ours in paper first then towels, laid it on it's side and cut the pot away. Had a 5 gallon pot ready, half full of soil mixture and picked up the plant and put it in the pot. I had more soil mixture with sand added to fill the pot. Wasn't to smart as I thought afterwards of putting the pot in a 5 gallon pickle bucket to be able to move it easier.
Makes it easier to use an appliance dolly to move then. You can do it!!

Thanks karmahappytoes. My primary concern is how to avoid breaks in the proces. Particularly on the really tall one.

Golgatha said: Thanks karmahappytoes. My primary concern is how to avoid breaks in the proces. Particularly on the really tall one.

Well one way to help mitigate that is to have at least one other person there with you if you went with the tip over method. The simplest method is to wrap it and then just break the pot off of it while it's standing upright.