diy sombre tips

Hello!

I currently have natural undyed hair (golden brown with natural sun lightened highlights) and then with very subtle bleached sombre lightening at the very ends that was done in a salon.

I'm going to cut my long hair shortish (sort of long bob/a tad shorter than that) soon and once that's happened, the tips of my hair will be lightened due to the beginning of the sombre.

I'd really like to put a light ash brown (revlon colorsilk) on my hair for a richer brown overall look (sometimes the natural light parts of my hair can look mousey), but keep those bleached ends light - how do I blend that box dye so that I get to keep the light ends and have the two colours nicely melted together?

Without any advice, I'm thinking just apply the dye from the roots and drag it down with my fingers avoiding the tips? I just don't know if that'll give me an odd hard line/patchy look?? should I maybe use a comb? *stars*

I'll add a photo if that's any help, although I couldn't find one with very good lighting (I'm the one who the arrow is pointing at!) and you probably need to have a good zoom in.

Sorry for the horrendous explanation !! Thanks for any advice 😀