The problem with a lot of good design is that it's a pain to clean it. Great design includes forethought on the cleaning department, if you ask me. So every few months, I find that despite my best borderline OCD hand washing, my Apple wireless keyboard needs a cleaning. After some research, I figured out that the best and possibly only way to do this is to snap off all the keys and wash them in a bowl of warm soapy water, carefully dry them, and then put them all back, one hopes each one in the right place.
It wasn't the original source of the method, but here's a link to a pretty exhaustive and visual rundown on cleaning your Apple keyboard. This model is no longer made, but I'm sure there are plenty out there. I cannot overstate the importance of having a photo or diagram of the arrangement of keys before you start the process. You can use the before/after shot above in a pinch. Since they letters on the keys are oblique (not italic, mind you), once they're off, there's some confusion between the L and the 7, and the I and the /, among others. Beware and stay clean.