On Slip

I forgot how irritating slip that comes in bags is. So far, I have not had the time to devote to mixing slip from dry clay, and have resorted to simply buying slip in the type of clay I need (for pouring into the plaster molds). It comes in two-gallon bags that you then have to somehow transfer to another container. I always forget that it's not going to be perfectly mixed slip and assume that I can cut a hole in a corner of the bag and pour it into a funnel over a couple of gallon plastic jugs. Inevitably, like today, I end up with the slip all over the place because it's thicker than I expected and won't go smoothly through the funnel or even through the hole in the bag sometimes.

Purchased slip is too expensive for me to have to deal with that kind of trouble every time I get it. Therefore, I am going to mix my own slip from dry powdered clay from now on. Does anyone else do this, and if so do you have any comments about which clay you prefer, or tips on the mixing and pouring process?