What's the best way to cleanup circuit boards?

The boards are coated except where they need to make electrical contact (green part = coated). Do not scrap off the green coating, but where there is no coating (brass color) use some fine steel wool (000 or 0000) but make sure you wipe off any steel wool pieces stuck to the board using very mild soap and water, and then dry it with compressed air. You can use the steel wool on the pins/post also, but don't break them off.