I think you've probably got under-exposed film. Film can get nasty casts in shadows where it drops off the toes of the different dyes differently, especially where the light is not white. Or if this is not right on the edge of blackness, your C41 process is out of control.

As to your question, why not just use the filters in the enlarger? Obviously (?) you're using a colour enlarger.

As to the colour to use, this is (unless I'm mistaken) counter-intuitive. If you were burning the hair down, you'd use a magenta filter to take out the magenta cast, but you're dodging. That means you need to use a more-magenta filter for the main exposure (including the hair) and then a more-green filter for everything but the hair to bring the skintones back to neutral. Look at it backwards: dodging the hair is the same as burning the face and background. So you pick a base exposure to get the hair right, then burn in the face and background with a greener filter to take out the green cast you introduced in the main exposure. Hope that makes some sense...