Flip them over stand on the handle of the top one and pull until your guts blow out. After you're out of breath and your testicles are about at your knees flip them upright. Spray a garden hose right were the 2 buckets meet and keep trying to fill the lower bucket. Eventually the top one will float up.
Hold the inner handle, blow down the side between them with an air nozzle, boom, they'll come right apart
That didn't work. Must not of had a big enough chit beater Air nozzle was the first thing I tried. Didn't work the top bucket had a crack along in the bottom. Water would have been the same results. Finally took a big big screw driver and started around prying between the buckets. Buckets are apart. I believe I will slip some thin cardboard on the sides.
That's a great idea...my luck would be some water would get in, the mulch would rot and make the best durned "bucket glue" ever!
I throw in a empty plastic coffee container in between them, ( not a drinking cup but the container ground coffee comes in) or a dis guarded flower pot to keep them from sticking together.
Anything that you can do to break the seal and let air in; sometimes knocking the top buckets back and forth while stabilizing the bottom bucket between your feet. I've used the screwdriver trick too. I'm pretty sure I've given up before and just thrown them out. Disclaimer: most of my experience is with the square cat litter buckets, so may not be as useful for round buckets.
I kinda forgot about this, but the neighbor (old farmer) showed me a trick a while back that he uses for bucket storage...he grabs a piece of used "small square bale" twine out of the back of his truck (there's always plenty!) and hangs it over the side of the bottom bucket, making sure the knot is in the bottom...the twine up the side keeps its from sealing well enough to make a seal/suction, and if they still wedge, the twine with the knot, now under the top bucket, gives you a good handle to pull it out...he said it works well...I never tried it since I don't have much (any) twine around my place most of the time...makes perfect sense though.
Flip them over and drill a big hole in the bottom of the outer bucket. Be careful not to go through the inner one or it will no longer hold liquids.