EDIT: Actually, there's a fun project for the technically adept person just waiting to surface here. If I were to build my own flour sifter, sparing no convenience or wattage, I would build one to fit my (your) mixer and bowl so that the flour can be sifted in without getting in the way of the planetary arm (assuming Kitchen Aid). I would also make it electric by mounting a small, cheap motor from the local Radio Shack, with an unbalanced weight attached to the motor shaft for creating vigorous vibration. The frame would be constructed as a stand that allows the sieve collar to hover above the bowl, being reenforced and weighted near the base for stability. Power it with batteries or an AC adapter, and you'll be sitting squarely in the lap of hands-free grain sifting luxury.
You just had to throw down the gauntlet didn’t you. . . .
OK, this is easy.
• Fashion a sieve (yes, collar shaped) to fit on the KA mixing bowl, but be sure to leave a little slop, i.e. a loose fit around the edge, perhaps 1/8 inch, so the sieve can rattle around just a little.
• Cut out the interior of the sieve in the shape of a cam, i.e. completely round, except for two small bumps inward, on opposite sides of the inner edge of the sieve, which will act like the cam.
• Every time the planetary shaft comes around, it will bump the cam, rattling the sieve first one way, then the other. This will cause a small amount of flour to drop into the bowl on each revolution.
• A little Teflon slider on that cam will insure that there will be no issue with the KA shaft.
This is what I call an eloquent engineered solution, because it works well on two separate levels. We get the “free” mechanism to run the sieve, and it adds the flour to the water slowly, like it’s supposed to. Bonus feature, no moving parts!
Unfortunately, I’m going to have to add this project behind the design of a gas fired, smoldering wood, temperature controlled horizontal smoker I’m currently working on. I do like the sieve idea though.
jack Edit: if this does not add flour fast enough, we can easily add a few more cams, or just run the mixer on setting 8 instead. <kidding>