imo, studiofixfluid does NOT work with the 190, or over prep and prime face.
prep your skin with a light moisturizer (studio moisture fix or strobe cream), and wait for it to soak in for about 10 mins. pour a tiny amount of studio fix fluid onto a palette of some sort, as a little goes a long way with this foundation. use the 187 brush, and dip is slightly into the foundation. i've used the 190, and various other brushes, NONE OF THEM COMPARE TO THE 187. using your 187, buff the foundation into your skin concentrating on one small area at a time, making sure that small area gets completely blended before you move on. once you've gotten all the "areas" of your face blened, go over your entire face lightly once or twice, to blend together the seperate sections. i've just found that doing it this way, focusing on one area of a time, gets the foundation blended better, as a whole. coverage is buildable, so if you notice that a certain section needs more coverage, go back and repeat the process. once you have your foundation done, grab a powder brush (i use the MAC #150), and spritz it lightly with fix+. tap a little loose blot powder onto a tissue or palette, and sweep the fix+ dampened brush into it. tap once, to shake off excess powder. buff loose blot powder onto skin, giving the studio fix fluid the perfect finish. blend powder all over face, then spray face lightly with 2 sprays of fix+. your skin should look flawless and it should stay on for pretty much the whole day. hope this helps.