Peroxide mixed half and half with warmish water. Swish it around for about a minute and than rinse with plenty of plain water or brush.
I've cleared an actual abscessed mess with just peroxide. Most dentists will recommend salt water because the taste of peroxide bothers a lot of people. Salt water gags me, and mixing the peroxide yourself is a lot cheaper than purchasing the glyoxide they sell OTC. After only two rinses you should notice a lot of pain relief.
Clove oil works too, although it won't clear any infection, it just works on the pain.