"how hard is it to mix the stuff"

It's easy to mix. Just four ingredients:
Metol
Sodium sulfite
Hydroquinone
Borax

D76H works the same as far as I can tell and you just leave out the Hydroquinone and adjust the Metol and Borax. Thing is, unless you want to buy Sodium sulfite in large quantities (20-50 lbs.) it is about as cheap to buy the Kodak stuff. It takes nearly a pound of SS per gallon of D76 and SS costs about $5.00 lb in smaller quantities. If you want the formula, try the Unblinking Eye site.

Dean