Contact WL good as ever

I own some quality HiFi amplifier brands Onkyo, Kenwood, Fine Arts. All are about 25 years old, but sound absolutely
convincing. The switch contacts oxidize over time and can paralyze the entire unit. I have the contact with the cleaning time
Time is wrong. Properly following procedure: contacts with contact WL properly fed spray, leave on shortly. Then I take an old boat piston pump with a narrow nozzle and blow with strong pressure the contacts dry, then lightly spray with mild spray, T9 or tuner spray that contacts. It works! Contact WL is super, it washes out residues and oxidations.
But you have to handle more then necessarily, otherwise there is an opposite effect. I hope this helps many longer version, the product is in any case deserted tip!