Interesting experiments. But consider the alternative: go ahead and buy a new keyboard after a few years of use. In addition to acquire all sorts of dirt over time the marking on the keycaps typically fades away on the most frequently used keys. A good keyboard should be no more than 20-30 bucks and you can get one for less than 5 bucks if the budget is tight. BTW, one of my USB sticks went trough a full heavy-duty cycle in the washing machine two years ago - and still works fine.