This is what I do..
I went to walgreens and picked up some of those pre moistened alcohol swabs that diabetics use when meassuring blood sugar or injecting medication.
I usually take one, squeeze some of the alcohol out if it is too wet and start cleaning the threading. Holding the swab tight on the threads and spinning the battery around.
Then I take a pin and go around the center post scraping out all of the green colored gunk that builds up in there. I wipe down the center post and inside thread part by placing the swap there and putting sligh pressure with my finger and give it a good back and forth spin...
Then I take the pin and clear the air holes and Im done.. Move on to next battery..