A white pen eraser works great on contacts. There is enough abrasion there to remove any residue without damaging your contacts. Do this to your positive contact and the top of your batteries followed by a Q-tip with alcohol . Apply Noalox or Deoxit to your positive contact. I never run my mod without using Noalox or Deoxit and I never have problems. Because I never run my mod without Noalox or Deoxit I have never had to clean my contacts with anything more then a Q-tip with some alcohol.