Being a retired barber I may be able to shed some light on hair growth.
If no hair is growing in a given area, and it started growing in the papilla today, depending on your hair's growth rate it would take 60 to 90 days for it to grow to the surface of your skin. You still would not see it as it must be beyond the surface of your skin to see it.
The only non-drug method that I have ever seen work in regrowing hair is a daily 15 minute scalp massage. Once it starts growing, you MUST KEEP MASSAGING your scalp! If you quit the massaging the hair will quit growing.
Hair is made up of carbon, oxygen, nitrogen, hydrogen and sulfur that is filtered out of your blood stream by the papilla in the base of the hair follicle. If you increase the blood circulation you will increase hair growth. Scalp massage increases blood circulation through the papilla.