In the summer, I generally only use a mineral based powder and that's it. The shade is slightly darker than my usual one so that it matches the change in skin colour. But I don't use anything underneath or over it. Mind you, I have had LOTS of laser so that helps. It also has an SFP of 15 which helps nicely and stays on all day and doesn't rub off on clothes either.
Perhaps you should look at a product called Dermablend, which is very good at covering shadow and it comes in a wide variety of shades so you will have no problem matching one to suit you. It's also waterproof and sweat proof so will stay on all day too.
You will need to blend a foundation over it to give it a more natural look, and again, use one that won't come off in the heat.
Nikki