From what I've read, it can convert to either testosterone or estrogen, so I would figure taking some type of inhibitor or "promoter" for one would help sway the results.
From Wikipedia:
DHEA has been implicated in a broad range of biological effects in humans and other mammals. It acts on the androgen receptor both directly and through its metabolites, which include androstenediol and androstenedione, which can undergo further conversion to produce the androgen testosterone and the estrogens, including estrone, estradiol, and estriol. DHEA is also a potent sigma-1 agonist. It is considered a neurosteroid.
To the original question:
DHEA personally hasn't shown a lot of change in facial hair for me, but I have heard minoxidil (basically generic/cheaper rogaine) works well, the 5% especially. It's worth a shot, but be careful.