It works even better with really fine gold...that's what i "invented" it for. It also works better with material all in the same size range...just like everything else: size matters!
Technique for you:
1. Set dish on a solid, smooth surface (tabletop not work bench)
2. Put the -100 gold (and not gold) in the soap dish
3. Include a very small amount of jet dry and water (add a little more if needed along the way)
4. Grasp the dish by the outside edges and move it in a circular fashion while still flat on the table. Speed up as you get the feel for it but high speed will not be needed.
5. When you stop the motion you'll see a tail of "not gold" to suck up at one end of your material!
Of course you can also use a backwashing technique with the soap dish. The super smooth surface means you can be both quick and gentle at the same time, important for -50 and -100 gold. You'll be surprised at how little water is needed for backwashing...if it's not working for you, take out some of the water!
Also, if you want to be compulsively thorough (like me!) whatever you suck out with these processes should go in a finish pan for reinspection.