My terrible experiences with makeup application have taught me to do the eyes first and then use a makeup remover wipes to clear up the mess and continue with the rest of the face. If you choose to do powder, don't just settle at brushing it away. Use a foundation sponge to press in some of your regular color (since the powder is a lighter shade), the lightness of the powder will blend with your shade and have a median shade.
Not into the equations and mixing colors? Take a photo with flash right before you leave. If you can, change the settings to be a brighter flash than usual to find all the errors. When I do that, I find that all my magical work with bronzer and blush is unseen, and I usually swipe on an extra layer or two.
What's your secret?