Advise needed.

While my dash is apart, I thought I would clean the inside of the plastic lenses for the gauges. To do this for the speedometer and tachometer you have to remove the small odometer and dimmer knobs respectively. I don't want to force or break anything so I thought I would ask if any of you have already done this and can tell me what I need to do to remove them. Do they just pull out? Do they unscrew counterclockwise? Do both remove the same way? What?