I have been using Deoxit D5 cleaner and ProGold G5 Conductivity and Conditioning Enhancer for overs 10 years without any sound degradation. For future cleaning, I would recommend following kit that has everything you need to clean the contacts,
https://www.musicdirect.com/equipment/caig-audio-video-survival-kit
https://www.musicdirect.com/equipment/caig-audio-video-survival-kit