How do you fix ashy porous ends?

Hi ,

I am going from a somewhat ashy dark blonde natural color and am trying to change it into a warmer light brunette shade. I even found the perfect brunette color - extreme light beige brown (level 6 blue gold base) from the browns extreme collection by l'oreal excellence. It is really beautiful vibrant light brown.

Problem is I did the strand test and my ends pulled kinds ashy since they are more porous from the summer sun where they were lightened. Would a protein filler help me? If so how do you do it? Apply to the whole hair or just the porous ends? Should I use a gold or red gold filler? I don't want the end result to be too red, mostly gold but a little red would be fine. Any advice would be greatly appreciated as I've never used a filler before.