Those chum can drive you mad...casting in front of and into massive schools over and over with few solid takes... Sinktip, a friend and I had good luck there a week ago with patterns and tactics 10 yrs in the making.
First, the small sparse pattern advice is good. I usually use a #4 or #6 short shank stainless hook tied simply with chartruse or silver crystal flash. Tie in the crystal flash at the rear with a small tail, wrap it forward, and tie off a small wing to the rear. A good alteration is to build a small head of chartruse uni-yarn and wrap the crystal flash back over it in either a shell back or bullet head.
Second, these fish take the fly surprisingly subtly. You'll see them lazily schooling...they are not on a mad frenzy until spooked and they certainly aren't on a feeding binge like coho after herring. From a tactical standpoint a floating line with a 4-6' leader works well. Cast out and let the fly dangle and retrieve in very short and or slow pulls. When you feel your line jerk back on a retrieve resist all inclination to set the hook...it's likely fouled. The typical take is a slow steady pull...the fish lazily takes the fly and keeps swimming. I usually apply moderate pressure, try to get the line on the reel, and then focus on getting a good hook set. Their mouths are so hard you need about 80% luck to drive the hook in to a place where it will hold, but it's a dandy when it does! An amazing amount of fish take the fly when it is simply dangling or sinking.
The honest truth is that the folks hooking up over and over again down there are fouling the fish. And no matter how hard you try you'll foul them too. But by being mellow with the rod and waiting for the right feel, you'll increase the good hookups substantially!