The radio buttons all seem to get sticky after years of use. You can try to clean them up, but they just get soft and deteriorate. The best thing to do is simply replace them. They pull right off. Get them here:
Radio Knob:Porsche Parts & Porsche Accessories - Wholesale Porsche Parts & Tequipment
For cleaning up the A/C control panel, use a soft bristle toothbrush dipped in some clear water and give everything a good scrubbing.
Rick