I guess it depends on what ds you go to.I have been to ds's that really hooked up shorter hair.The would curl it with different sizes of curling irons and shape up the nape.
Then i would go to ds that would just wet set short hair and pick it out..having the poor child looking like someones grandmother..
.(helmet hair).
If you are interested in the the deep conditioning services of ds..just simply buy you some dominican conditioner.My new fave(until my hair gets sick of it)is tropical de bano creme milk protien conditoner.Make my hair soft,shiny and detangled.
And to the question do ds help in hair growth...well depends i guess.When i started going to the ds my hair was damaged and about shoulder length.I always had long hair as well but it just wasnt healthy because of all the abuse i did to it.. so it wasnt growing at the time.After a few months of just getting a wet sets, having the roots blown out,using dominican products my hair grew to a healthy back length.
I wasnt expecting this to happen..but i did notice that in just about every ds the women had beautiful long healthy looking hair.