i have been trying few mixed fermentations for a saison. i've never quite mastered the dupont yeast, at low temps it packs up early and at high temps it tastes awful in my experience, so i have been pitching dupont + brett strains and fermenting at cooler temps (tried dupont + brett brux at high temps and it was like sniffing glue; funky headache), so some of the saison character is there but the bretts take over and clean up. i don't do cell counts so i don't know the exact ratios but the best result so far, for a nice dry mellow farmhouse base beer that took various dry hops nicely, was a normal pitch of saison and smaller equal pitches of the three brett strains i keep in my freezer library; wlp brux, lambicus and trois strains, fermented in the 22-25 degree range. there's no method to my choice of strains, i just chuck 'em all in together with the sacc.