Hair Growth Remedies

I lost the hair on the top of my hair due to radiation and I was wondering if there are any special treatments I can do to promote the hair growth.
Should I wash my hair more or less? Right now I have some dry scalp so I use an all natural itching/dandruff shampoo that has been helping. Also, I wash my head twice a week and use a soft bristle brush to remove the dead skin and stimulate blood flow to my scalp.
Any recommendations?

I was reading some question and i saw that lavendar oil helps with hair growth if you use it to massage your hair.
How many times do i have to massage it?
And how do i dilute it?