Good way:
Cornrows (not too tight) with NO braided extensions attached would allow you to wash and moisturize often. My little sister braids her own cornrows, and her hair's growing fast and healthy. It's not relaxed. Find a gentle, patient braider.
Not so good way:
My hairline and edges thinned from excessively tight cornrows. I'd go home from the braider and latch braided hair extensions in that were too heavy, so that strained the follicles even more. Plus, I didn't take care to wash my hair during the ~2 months I had the braids in. I didn't relax my hair for a couple of years there, so I guess it was strong enough to take the abuse. But my hair's been shoulderblades length FOREVER because every 2 months I'd just let the braider wash and blowdry and comb (rip!) through my natural hair. She was rough and disliked dealing with my foot-long 4b afro. She just wanted to get it over with. It was an unhappy cycle for me, so I quit the cycle and the braider.
Note: Synthetic hair (typical plastic hair for braided extensions) is coated with chemicals that dry out the real hair and make it kinda brittle. My new stylist says it's a common preservative containing formaldehyde.