Curing damp concrete create vacuum against any airtight mold..
This creates much of the initial 'stickiness' and release film doesn't help.
Small holes drilled in your molds will help tremendously in it's removal by elliminating much of the vacuum..

That said a great release film is mineral oil and vegi oil mixed half and half.

If you do have a vacuum problem try this.
Press a vacuum cleaner hose tightly against the damp tufa attached to the exhaust so it BLOWS air. It will push air right through the damp tufa and release the vacuum of the mold. Often the mold will just pop off.

Try Cresset release products.I've used them for 3 years without any problems on plastic,metal,urethane and latex.Search their web for your local dealer.It ain't cheap but,if you're in for the long haul,give it serious consideration.

Drilling holes helps a bunch, I also use silicon spray,pam,or pledge. If you use anything glass or metal, be sure to line with plastic bag , or you will have a bowl full of crete sitting around :-)
bonnie

If I'm really worried about release I line the mold with a plastic bag; I've used silicone spray or just brushed motor oil on the inside of molds (lion's faces, etc.), or just put some oil in the mold and swirled it around until I felt all the nooks and crannies were covered; then had no trouble with a release.

I've had a devil of a time with some big items releasing even with the plastic bag until, like Dave, I got the idea of drilling a hole in the bottom and the thing practically shot out of the mold.

Also, in a fit of genius, I made one in a straight-sided, metal mold and with or without the plastic, there it still sits today -- a pan full of crete -- makes a good doorstop tho. :)