I see many comments on cleaning up battery terminals etc. I do not see any on the best way to actually do this. What would you recommend for cleaning :- Battery contacts and the in-camera contacts for these. The connecting terminals/pins on a grip attachment - the ones that transmit the "instructions". The AF contacts on the camera body and the back of the lens. Have had grip problem recently and would like to do a full "spring clean" - so thanks in advance.