I accidentally spilled beer over the left portion of my Filco tenkeyless with browns.
I disassembled it as far as I could to find out the obvious, you can't really disassemble the switches themselves, which had had a beer injection. The beeredness of the switches made them hard to press the first few times after you hadn't typed a while, causing password typing havoc, and they also released a bit slower.
Anyway, I tried some 96% alcohol, I used a Q-tip to put some on the switch while it was pressed down and then rocked it some. It works for like... a few minutes.
Here comes the answer I knew beforehand would come out, but tried to deny.
WD40
The answer to all of man's problems, McGyver's McGyver.
FYI, a WD40 spray can puts out a lot more than you need for a single switch, I used a box cutter (because it has an appropriate shape) and sprayed that, whiped off the excess and applied it to a pressed switch.