I have tried two different crock pots and couldn't use either because they kept getting too hot on the outside. So I improvised and used the oven. I decarbed the trim first (check out badkittysmiles in the cooking forum) then after it completely cooled, put it in a dutch oven with the butter and set it at 200 degrees. It was in for about 12 hours. Let it cool enough to touch and squeeze it through a couple layers of cheesecloth (you can get in the kitchen gadget section at Safeway). You can squeeze more out by squeezing about a handful at a time. But that is pretty much it. Just one of many ways. I am going to be making badkitty's recipes as soon as I get a bag and some dry ice to make some hash. Wow, sorry for the book.
Oh yeah. I used 8 sticks of butter to a little over 3 oz trim. Ended up with 3 cups butter. I just couldn't squeeze anymore. You will prob get more.