Here's my answer. Use an auger to press the stuff thru some plates with holes in them. Minimal mixing is needed to just get the corn starch sort of wetted with silicone. Then inject it into the auger, turn the auger, and out comes uniformly mixed Oogoo, ready to mold.
Please see Thing84579 on Thingiverse.com for files and details to print your own.
Using your Oogoo Mixer:
The video shows how to use the Oogoo mixer. Here's a summary:
Sift the corn starch.
Assemble the auger and feeder.
Squirt about a tablespoon of silicone into the Feeder.
Spoon in some corn starch. (Exact quantity doesn't matter. I try for about 1 tablespoon of silicone and ½ to 1 tablespoon of corn starch.)
(As an experiment, I added some water color paint, which worked great. I want to try other colors.)
Mix the Oogoo a bit in the Feeder so the plunger can push it.
Push some unmixed Oogoo into the auger case and turn the auger. Be sure the opening mark is lined up again.
Push some more Oogoo in and turn again. If you push too hard, it squeezes out of the Feeder. No big deal.
Repeat until all your Oogoo has been pushed through. You should have some uniformly mixed Oogoo at the discharge end of the auger.
Pull out the plunger and reload with silicone and corn starch, if necessary.
When you have enough Oogoo mixed for your project, scoop it up and use it.
Cleanup is easy. Let the Oogoo cure for 5 to 24 hours and just peel and rub the stuff off your feeder and auger. Happily, it doesn't stick to PLA plastic. ( I haven't tried ABS, but I expect it's the same story.) Use a dental pick or thin wire to clean out narrow openings.
When the Oogoo has set, open your mold and clean up the casting.
Plan your next Oogoo project, knowing you can do the mixing quickly and easily!