Here is a quick interview with Gordon Espinet VP Global Makeup Artistry MAC Worldwide, on Mineral Makeup 101 and on how to apply:

Q: Why is mineral makeup such a huge trend right now?
A: For a long time, women have wanted an alternative to the heavy powders and foundations that are on the market. They want their skin to be flawless but not made up and mineral products fit that need. We of course still have plenty of customers who cannot live without their full coverage, but that is why M·A·C is the makeup authority, we have something for everyone. It’s about having choices.

Q: Do you apply mineral makeup differently than non-mineral makeup?
A: Mineral makeup is no different than any other makeup when it comes to application techniques. The difference is in the final look. Mineral makeup provides a more natural appearance and always looks perfectly applied. As with all makeup, be sure that you choose the correct colours and begin with less product as it is easier to add product than it is to remove excess.