I feel your pain. My skin is super sensitive and really prone to red bumps and ingrowns if I'm not extra careful. Waxing is really the best option to avoid razor burn completely, but if you can't do that, then at least make sure you exfoliate really well before you shave and use a single blade razor with a sensitive skin shave gel like Aveeno's. Change your razor often and try to go over the area lightly and as few times as possible.
Here's the kicker... if you can stand the sting, splash the area with a little rubbing alcohol as soon as you get out of the shower. It'll definitely hurt for a second, but it'll disinfect any tiny cuts you might get while shaving and keep the area from getting infected and turning red. TendSkin works too, but seeing as the main ingredient is alcohol (mixed with a few exfoliators) you can save yourself some money by just using regular rubbing alcohol.