Red Hair To Blonde

Hello! Glad to be a part of this lovely forum.

So I have a friend and we want to bleach her hair blond, but like really blond, platinum if possible. Here are the facts:

1) Her natural colour is very dark brown and her roots are showing.
2) Her hair is a bob and reaches her jaw.
3) Except her dark roots, the rest of the hair is dyed red. She hasn't dyed it for about a month, BUT, I did use a pink semi-permanent dye on her a week ago.
4) She has been dyeing her hair red for over a year now.

So next week I'm turning her into a blond. My plan is: I use a hair bleach with a 20-volume peroxide for 35 minutes, and then I use a silver toner so we can achieve a good result.

I am not sure about the process however. Should I dye her roots first and then the ends, or vice-verca? How much time should I leave the silver dye/toner on her head? Is it correct to leave the bleach on her for 35 minutes, or is it too much?

To ensure that her hair is in perfect condition I've told her to use a hair-mask everyday for one week and leave it as much time as she possibly can. That's a good method to protect her hair right?

Please give me as much feedback as you can. Thanks for reading!!