I use RCBS case lube 2 too. As the other poster said, it is water soluble, and in a pinch, you can clean the final film off with a trace of spit.
Imperial cleans off pretty well, but there is a petroleum component that stays on the case if you just wipe it. It does come off with alcohol. I've also sized a few cases, comparing Imperial against RCBS, with the same die setting, and they are sized more with the RCBS. In that sense, it is a "better" lube, but of course, all you have to do is reset the die. Consistency is what is most important. YMMV