Hi-end contact cleaner and lubrication liquid/spray for hi-end audio or electronics. Expensive but it works. Full range of products only available in USA. HK got only a few.

DeoxIT® D-Series DN5 Origin: USA

DeoxIT® Gold, Gx Series, GX5 Origin: USA

DeoxIT® Fader F-Series Origin: USA

FLEX-TIP™ - Extension Tube Origin: USA