Extreme Grey to Blonde

I need someone with major color experience to help.  I have a client with really short grey hair and she really wants to go blonde.  She has some areas that are white/grey and others that are dark grey.  So, any suggestions?  I wasn't sure if anyone had any experience with this type of base going alot blonder.  I wasn't sure if it would be best to bleach and tone or use High Lift.  Obviously, Neutral covers grey the best but.....well, lots of questions.  Would love to hear ideas.  I am most used to using Wella products......

Thanks, Brian

Hey bnb; you may have to treat this head like it's two different ones! In the areas that are darker (don't know her natural level), there is more of her natural colour showing through along with the grey. You could use a light blonde neutral ash or ash on that part since the dark will come up brassy. On the white/grey areas (less pigmented natural hair), you could use a light blonde neutral with 20 volume. Of course, you could just bleach the whole thing altogether or use a light blonde neutral colour on the whole head & cover any brassy spots with highlights.