Key not working on Access Polar

[KaareDK]

Hello guys and girls

I im the proud owner of a polar.. its my workhorse and i take it everywhere i go. Lately som of the keys has started behaving odd. The lowest C note is not working properly.. and the mid D# key is totally dead.

I found a turtorial here on the website, regarding how to clean the contacts, but the link is dead and the instructions provided by a user are no longer to be obtained...

Can anyone pls tell me how to clean the contacts o my virus keyboard? I suspect that the keys are not functioning due to dirt.

thank you very much!