- cotton swabs (better the double headed plastic ones)
- alcohol (better isopropyl)
- pressure plier (like those husky locking pliers or similar)
Flatten the cotton head using the plier enough to be able to fit tightly into the USB slot. Don't flatten too much - you want some resistance to guarantee a nice friction. Dip the cotton into alcohol, insert and give it a good rub - until the the metal contacts start to shine again. Avoid alcohol sliding into the electronics keeping them upside. Flatten another cotton head similarly and dry everything. Wait at least 10 minutes for the residual alcohol to evaporate.
Enjoy five more years out of your gadget!
ps.: if the metal contact was exposed, an eraser (or rubber) would do a better job, especially that blueish one used to erase ink from pens.