Throw all into a food processor, and whirl until you get a paste of the desired consistancy. I usually rinse the canned beans to get rid of the extra salt. Depending on how well its been drained, I might need to add a couple extra TBS of water. On the other hand, I also like it a little dry, so when I get that urge, I'll forgo the extra water and process it so that its a little chunky.
I've been using this for lunches for a couple of months now, and love it.