The industry standard way of cleaning contract is with IPA aka isopropal alcohol the stronger the better. Look for 99%. You use this with a natural hair brush. Like a horse hair acid brush. Using esd protection you rinse brush and rinse again. Blow dry do not let air dry. You can use lint free cloths for the fingers instead of a brush.
Never use an eraser it'll leave behind a film and is abrasive. It'll cause problems eventually. This is how it's done at IBM and most other companies. If you can't get 100% IPA then 97 will suffice.
I used to have problems with the daughter board not seating properly in my 3000.
