I went through the "growing-back" thing after a head injury years ago. The hair came in nice and new and healthy, of course, but I can't say it grew any faster than its usual rate of growth. Not that you've implied you can, but (for readers) you can't make your hair grow faster; but you can prevent damage that either makes hair look short/thinner or else amounts to needing to cut the hair sooner than you otherwise would have had to.
Whether right after the head injury or in the thirty-plus years that have followed, I've generally always washed my hair every day (although taken a day off here or there once in awhile) with a mild shampoo. Mine isn't hair that needs conditioner very often, but I think if the hair starts to get "tanglier" (which can require ripping through it to get tangles out), a mild conditioner is called for.
Other than that, I'd say stay away from chemical processing (at least as long as you want it to stay as healthy as it can) and things like curling irons and/or blow dryers as much as possible. I don't think occasional use does a whole lot, but regular use does. If you can stay away from too much use of things like elastic ponytail fasteners or any hair accessory that puts stress on the hair. Trimming off any split ends regularly eliminates the chance the hair will look shorter because of a lot of split ends. A diet that includes plenty of nutrition and lots of water are said to help result in healthy hair too. Brush or comb it gently, and if you run into a tangle carefully separate the hairs (rather than rip through the tangle). Also, limit (or protect the hair from) too much (too regular) exposure to swimming pool chlorine/chemicals and drying sun/weather.
I've always seen washing daily very differently than a lot of people do. To me, a healthy scalp is a nice, clean, scalp. Not long ago, I learned an interesting thing about the hair in the eyebrows; and that it is that if a person gets face moisturizer in the eyebrows, the eyebrows may stop growing in at all. To me, this backed up my belief that a scalp that clean of all shampoo residue, moisturizer, hairspray, and/or oils might stand a better chance of growing hair better than a "smothered" scalp might. That's nothing more than a personal guess/opinion, of course - and I'm not pretending it's anything other than that.