While it's not exactly what you were asking about, I mix high gloss clear with my "colors" and get a translucent/mottled shade. For whatever reason no matter how mixed the powders get, I get that mottled look. It's a full coat every time.
When I've mixed solid colors, the first batch will have each color intermixed where you can see each. After that it's a solid mix. This was mentioned already.
I may try the salt shaker/paint brush trick. When you do that with a red color, I'm quite sure the bullets would be faster and possibly more accurate. I'll try it with parchment paper instead of my silicone mat so I don't get the mat to messy.