It's a pain in the neck cleaning the buttons if you ask me, since you have to remove the whole motherboard to access them. Before going that far you might want to actually try using something like a toothbrush or a toothpick to clean around the buttons with a little bit of alcohol before opening the console up. It might be good enough to dislodge any dirt stuck in there without having to open the console up at all. However, if the problem is that there's dirt underneath the contact pads on the motherboard itself, you would have to fully disassemble the console to lift them up and clean underneath, since no amount of scrubbing from above would fix that. Usually this would only happen with liquid damage though, so it's more likely you just have some dirt accumulation.