To get an airbrushed look to your foundation, use a stipple brush or sponge with a liquid foundation. Apply the foundation using the brush/sponge with the stippling method.
The only way I apply my foundation is with a stipple brush. I used to use cosmetic wedges, but those went bye bye as soon as I got a stipple brush. I love how my foundation looks when I use a stipple brush, it looks airbrushed and flawless. My stippling brush is one of my favorite brushes.
The most important thing to have with stippling other than foundation is a stippling brush or sponge. You need to have one of these in order to stipple correctly. I recommend using ELF's Studio Stippling brush
or the Beauty Blender stippling sponge
If you don't want to shell out the money to get the Beauty Blender, there are dupes available.
Once you have the right tools you need your foundation. A liquid foundation will work best. Put the liquid foundation onto a palette (a pallet like a painter's pallet not like an eyeshadow pallet, I recommend using the shiny side of a CD or an itunes card. Make sure they are both very clean before using) then dip your sponge or brush into it.
Next comes the actual stippling. The stippling method is very easy, though it may sound confusing when explained. Simply take your stippling brush/sponge with the foundation on it and bounce it up and down all over your face. You can do it as many times as you like to get preferred coverage. This method will also help you apply your foundation evenly.
Lastly, after stippling you can buff the brush or sponge around your face in a circular motion to help blend it all in.
I recommend using a setting powder when you are finished, I always set my foundation. I recommend using a translucent powder such as Elf's High Definition powder
or Makeup For Ever's HD Microfinish Powder.