A thorough gargle/rinse with a mouthwash (e.g., real Listerine, that contains alcohol) will go a long way, and then swallowing some fresh mouthwash will rinse/disinfect the throat. This method isn't perfect, but it's better than letting fresh cum sit for a while on the very porous membranes of the mouth and throat.
It does require some preparation. If you're hooking up at home, you'll have what you need; if you're out somewhere expecting some fun, you can pack a small travel bottle of mouthwash in with your lube, condoms, poppers, and/or other toys.