I bought some Chem Dip. This may seem like a really dumb question but how do I open the can? Do I cut the plastic rim off? I tried pulling if off by hand, with a pry bar, and driving if off with a hammer. I can't figure out how to get the can open. There are no special intructions that I can find. I Googled this and the answer was it should open like a paint can. I don't think so. Not unless maybe I cut the plastic rim off first.