Man if you have beard dandruff you probably shouldn't have a beard...
Besides a couple occasions for maybe a total of a half-year, just because I felt like switching it up, I've been rocking my beard since Fall 2015 (I'm currently on a switch up for the last month but I'm growing the beard back). All I do is wash my shot consistently every night, grease it with Cantu, and comb/pick my shyt out. Most women I've been with love my beard but I did it for me because that shyt looks damn good on me...
That Cantu be having my shyt glistening and smelling right, sometimes I forget to grease it and my shyt still look healthy because I wash it. Thats all I've had to do, thats me in my avi, can't really get the best view of my beard because its a black and white picture and my beard isn't at full growth in it...
But I dont have much advice on dandruff bro, never got it in my beard. I dont fukk with any of that beard oil shyt, women will try to sell you on it and maybe that'll help with dandruff? But I never needed to use that Miracle Gro ass shyt...