How to clean up a gunked up power button?

This also applies to pretty much any plastic button cover for phones and tablets.

Quick Note: This is NOT a question about the soldered on portion of the button.

Recently received an S II to fix. Thought the motherboard was busted, but it appears that the power button cover is merely gunked up around the sides inside the case. One of the stretchy bits that holds it down inside is also torn, and the other is stretched out. But the main issue is the gunk (not sure what it is). My problem is its such a narrow space between the cover and the case. Since the cover is already somewhat detached, im tempted to pull it out from the inside so i can clean the hole. But in the future, i'd ideally want to avoid this. Anyone successfully cleaned that inbetween place? If so, what did you do?