It's unreal. Instead of a painting motion, you do little circular motions and buff your product onto your skin. It gives a flawless, airbrushed look to your foundation and it perfect for scooting over uneven skin or acne. Think of it like applying foundation with the 187, but because the SB brush is designed to have a little more resistance it gives a smoother look much faster.
It was designed to work with the SB hard cream foundation so it's fine to use with creams, but it's also divine for liquids. I used with Hyperreal and it left no streak marks or splits.