I think it really depends on each person. Since I started HRT, I've had fast progress with everything.
With hair specifically, when I went full time I started shaving under my arms, my arms, hands, chest, belly, legs and feet. I was pretty hairy. After about a month of shaving and about four months of HRT, my arms, hands and feet only grow fine blond hairs, rarely ever any course dark hairs but they pop up occasionally.
I couldn't shave my back but it was really hairy before HRT. I can't feel any hair on the portions that I can reach. My wife told me that I only have a couple of small patches left. The hair on my butt is either fine and blond or non-existent. The hair under my arms, on my legs, chest and belly have started growing in more slowly.
Amy