I use a touch of Alox type bullet lube, while the mold is hot.
There's a guy in Alaska, who's on the Cast Boolits forum, that sells a sprue plate lube that's supposed to be just the thing for the Lee molds.
I'm reading the LEEmenting thread right now and saw the link to that guy's sprue plate lube. I'll go the route with a proper recommended product, but just wanted something cheap and short term that wouldn't burn up or polymerize, and I could get right away and does not require mail-order.
This is my single-cavity 12ga 1oz shotgun slug mold. I was kind of worried about it because it's actually a three part mold with the split cone in the middle to make the drive-key bar across the deep hollow on the inside of the slugs. Even LEE's own instructions talk about sanding it if slugs won't drop free, because besides the halves they can hang up on the center cone and bar. However, out of the first 110 I did, only one had to be pried out with an awl and tossed back into the pot. The rest dropped nicely into the folded towel pad I laid out.
I do see what people say about Lee molds being "adequate" but not the best. At certain temperatures, the halves didn't line up quite 100% and I had slugs with extra sprue and flow that went out the bottom of the mold at times. However, for $18 I'm not complaining, and just tossed those ones right back in the pot, and closed the mold more carefully.
I use a tiny bit of high temperature grease, applied with a matchstick. (and I don't smoke the mold cavities)
I only smoked it twice, at the beginning, and halfway through when it started taking more than two or three whacks to get the slug to drop free of the center cone.