The fact that your hair is in braids does not mean that you should not wash it.
Just as you would wash your hair when it is not in a protective style, you also need to wash your hair when it is braided to keep it from smelling.
If you are planning to wear your braids for as long as 8 weeks, you should wash it at least once.
This would help to keep your scalp clean and it would help your hair to grow faster.
Here is how to wash your hair in braids without wetting the whole hair and making it rough.
Section the hair into four or five parts using elastic hair bands.
Wet your scalp only by holding one section of braids with one hand and rubbing water on the scalp with the other.
Take your shampoo and lather it up in your palms.
Use your fingertips to massage the shampoo into the scalp and wash the scalp using the fingertips only.
Rinse the scalp by bending forward, holding the section of braids in one hand and pouring the water straight through the scalp.
Use a towel to dab the hair when you are done washing all the sections.
Oil your scalp gently and wear your braids down so it can dry.