GrowHairLikeStalin said:
Do you recommend using Retin A at all???
I'll give you a qualified "maybe" on that!
Retin-A has been shown to increase the absorption of topical minoxidil, apparently by decreasing the thickness of the outermost layer of skin/scalp which serves as a barrier to such absorption. Furthermore, it's even been shown in one study (see abstract below) to have hairgrowth-stimulating properties
of its own, when used all by itself (without any minoxidil at all).
However, people have gotten into a bit of trouble by using Retin-A on their scalps!

Guys who post on hairloss sites like this one can't seem to resist the temptation to use too much Retin-a, sometimes with very bad (dare I say HORRIFIC) results. Excessive Retin-A will most assuredly cause irritation to your scalp, and if you use waaay too much, the results can be frightful! Use it ONLY if you have enough sense to use the proper dose, and don't go overboard with it!
J Am Acad Dermatol. 1986 Oct;15(4 Pt 2):880-3, 890-3.
"Topical tretinoin for hair growth promotion"
Bazzano GS, Terezakis N, Galen W.
Topical all-trans-retinoic acid (tretinoin) alone and in combination with 0.5% minoxidil has been tested for the promotion of hair growth in 56 subjects with androgenetic alopecia. After 1 year, the combination of topical tretinoin with 0.5% minoxidil resulted in terminal hair regrowth in 66% of the subjects studied. Tretinoin was shown to stimulate some hair regrowth in approximately 58% of the subjects studied. One female subject with pronounced alopecia for more than 20 years had regrowth of hair using only tretinoin for a period of 18 months. Tretinoin has been shown to promote and regulate cell proliferation and differentiation in the epithelium and may promote vascular proliferation. These factors are important for hair growth promotion. These preliminary results indicate that more work should be done on the role of retinoids in hair growth. The synergistic effect of retinoids in combination with a low concentration of minoxidil should also be further investigated.