Not only turn off, but switch PSU power off in back or unplug. Some systems leave the +5 USB voltage active when powering off.
Should be no problem as long as carefull and LEAVE powered off until POSITIVE all Alcohol and water have evaporated. Other 10 % is distilled H2O and takes longer to evaporate. My self I'd probably not use a tootbruch, maybe a pipe cleaner (gentially).
A toothbrush might be abrasive and scratch the contacts. I use compressed air for cleaning out ports. If it still works, there's nothing to worry about.
As soon as I saw the title that's the first thing I thought of. It will probably be ok but next time I would just use compressed air. If you really need to clean it out you can try a q-tip moistened with rubbing alcohol but as said make sure the computer is off and UNPLUGGED. Also make sure it is compleatly dry before you go sticking a USB device in there.
thx guys i just dont wanna mess up my usb ports, im thinking it might affect the ports or something and that would be horrible since i like to play counterstrike competitively