Using Masking with a Brush to make Selective Adjustments

I am still new to Color grading and am using some presets to start me in the right direction. The presets seem to be adding a bit too much orange and red tones to the skintone and too much saturation. I tried using Masking and a Brush to paint over the face so I could adjust some settings that would only apply to the face, though it still applied it to the whole image. What do I need to do to make these types of selective adjustments?

Thanks