Painting realistic hair in acrylic?

HI, please ...HELP!! First time I'm using acrylic. I'm painting a close up of girl with hair blowing in the wind. Her head size is 30 cm and I need help with her hair.My base colours are burnt umber and burnt sienna mixed with white - how many base colours are needed to build depth and can you suggest colours to use considering the over all hair colour is reddish - light brown .After I've laid my colours do I glaze over (smudge) everything with white to blend then add definition colour and repeat glazing with white?Then use a no 2 brush to slit hairs?How do you get realistic hair?