1. What is most effective when applying...sponges? foundation brushes? fingers?
I find that using a wedge sponge works best. The foundation brush will leave texture marks in the finish, and it's too thick to apply evenly with fingers. At least that's been my experience. Powder is key to getting a long lasting setting for these foundations.
2. Can these colors be mixed easily?
No, if you try to scrape any of these out of the pan, you will notice the texture is much thicker and more solid than most creme foundations. They just won't blend together very well. But honestly, with the 32 shades that are in those two pallettes, I've never found myself needing to mix. There was only one occasion where I didn't have a good match from those colors. It was an African lady, whose skin had a bluish undertone. It wasn't like any color I had encountered before then, or since. It's definately not a common skintone in my area.
3. How do you use the foundation thinner? The site suggests applying some to a sponge, but what works best for you?
I apply the thinner directly to the sponge, then swipe it out the pan.
SOme other things I have noticed about RCMA... They work better when they are slightly warm. I have taken to setting mine near a warm windowsill, or leaving them in the trunk of my car for about an hour before I need to use them. Alternatively, I have also just patted them on the skin, then let the foundation warm to body temp. for a few minutes before blending. Either method works, but the first are a little faster if you know you are going to need to work quickly.
I generally get 8-12 uses per sample pan in the palette. My method is to use it first at full strength as a concealor, then use it diluted with the thinner over the rest of the face. I am pretty light handed with foundation, regardless of the product I'm using. If you tend to apply more heavily, you will get less use per color. When I run out of a color, I buy a full size pot, and just smoosh it up in the pan. It's much more handy than carrying all of those full size colors everywhere.
My best advice is to practice using them many times before you try them out on a paying client. Since the texture is so different from most foundations, and the pigmentation is much more than usual, it might take a few tries to master it. I know that I tried about 4 different methods on my very patient friends before I found a method that produced a natural finish that I was happy with. If use too heavily, the skin will look a little to perfect (artificial) , and waxy.
It is worth the effort. I love the way these photograph so beautifully, and can still look believable in person at the same time. Those little slim palettes are so handy, and it definately beats carrying 20 or so other products around in your kit.
Hope that helps.