With studio fix, I have tried:
182 kabuki
183 flat kabuki
187 duo-fibre
188 small-duo fibre
190 foundation brush
191 square foundation brush
my fingers
mac sponges
sonia kashuk version of the beauty blender
unfortunately... i have yet to find one that i consider my like "holy-grail" applicator. i'm beginning to think that perhaps it has more to do with the person operating the brushes (i.e. me) than the brush themselves. one of my sorority sisters works at Mac and I was telling her my issue with foundation application and she said that I should try holding the 190 foundation brush at the end of its handle and kind of dab/stipple the foundation on. I started doing that, followed by blending with the 183 flat kabuki and it seems to be working pretty well, except now I've realized that I think i'm wearing the wrong foundation color!!