Braiders always say you can't wash cornrows, only individual braids, so I never used to, but then I tried it and it didn't wreck my braids at all. I was just very gentle. I got my head wet in the shower, then I diluted some baby shampoo with water and applied it very carefully to each parting, got it a bit wetter, and then let the water rinse out the shampoo. I then blotted the top of my head with towels by pressing down to press the water out. Then I sprayed a spray-in leave in onto my hair and very gently oiled the parts with my pinky finger.
Get used to me. Black, confident, cocky; my name, not yours; my religion, not yours; my goals, my own; get used to me. -Muhammad Ali