Going from dark brown to natural looking ash brown?

[michelleivette]

My hair is currently this color with some golden to medium brown highlights

and I want to achieve a brown like Miranda Kerr's (without her highlights):

How would I go about doing this? (Also, what color dye should I get) It's not an option to get this done at a salon, my friend is licensed so she would help me out. Preferred dye would be Wella. Thanks!