Best way to fix a flat is to get rid of it and replace it with a new tire of the same brand ,LR.and tread design. The inside patch is the best way to patch it,but I wont run a patched tire any further than I have to to get a replacement. A patch job would be OK for a spare,butthat would be it.
You loosen the lug nuts on the flat, then pull forward or back up onto the ramp with the other axle's tire, leaving the flat dangling, pull it off, put spare on, tighten lug nuts, move trailer down off the ramp, and retighten. No jacking required.
These do not work for all dual axle trailers. My old tt had the wide stance. I drove the front tire on and the rear tire stayed on the ground. Had to Jack it up instead.