Me and my parents used to rescue garter snakes that had been hit by lawnmowers and stuff all the the time and triple antiobiotic gels (such as polysporin) used to work very well keeping them from infection and helping them heal, though we used to just use the generic brands.
Dunno if this was the right thing to do, but it worked well for us *shrug*. None of our snakes succombed to infection or died and a couple were very badly injured to the point we thought they couldn't be saved.