The powder stuff = cal? I don't know about using that to prime a pot. The only uses I know for cal are for turning corn into hominy, and also to "paint' a clay comal to keep the tortillas from sticking.
(Be careful with cal -- it's slaked lime.)
The clay pots from around here are glazed on the inside, so they don't leak or sweat liquid. As far as I know, you only need wash the pot well before the first use. You could let it soak in water a while, as with a clay flower pot, if you wish, or just boil some water in it on the stove. Sorry ~~ I don't feel like I was much help.