Matrix formula advice

[eilsxx]

Hi geeks -
Looking for some advice. Currently my client has level 10 hair (heavily highlighted with about an inch of level 8 roots) She's naturally quite ash and has shown me this photo

. My initial thoughts were to go in with an 8P all over , rinse, dry and then balayage with bleach and 3% to obtain the desired result.
Looking for some reassurance with the 8P or easier methods to do this in one step.
Sorry if this is a silly question - late night brain and not too long qualified!
Thanks
x

 

[eilsxx]

Also concerned the 8P might come out a bit too grey. Lol

 

[cassies97]

Why 8p that pic isn't an 8?

 

[eilsxx]

Why 8p that pic isn't an 8?

Hi sorry my knowledge is not the best but my method was I matched up her roots which were an 8 through the front and a 7 in places through the back and matched her up to an 8P, as colour sync tends to run a shade darker I thought this would be alright?
Apologises if I'm going the complete wrong way about it , can't think straight [emoji23]
What the Christmas rush does to us all haha!

 

[eilsxx]

Sorry should of said the 8P matched up to the regrowth st the back which was a level 7 not the lighter regrowth