Quick hit for the hive mind. I've been getting my hair professionally color treated for about 2 years now (I used to be religious about doing it myself, but after a single disastrous attempt at going from dark brown to Joan Holloway copper, I became gun shy and decided to leave it to the pros). Three weeks ago, I decided to try red again in the form of a soft, lightish auburn. It turned out fine, but I'm just not crazy about the color and would like to go back to my rich, chocolate brunetteā€”so darker a level or two. I really don't want to pop $100 again to fix this, so I'm considering going back to my at-home roots (ROOTS. GET IT? ROOTS).

Any tips on how to do this safely? How long should I wait before battering my hair again? My hair is fine and sheds like crazy, so I have irrational fears that one bad round of hair dye will leave me bald. Any tips on color selection? In terms of selecting tones, what undertones would you recommend I pursue if I want to keep the warmth of the red without it becoming kind of brassy-too-golden-auburn-no-thanks? (And yes, I will be doing a strand test!)

For reference, I have fine, somewhat wavy/sort of straight shoulder-length hair, and rarely use any sort of heat styling. Before I went red, I had some subtle ombre highlights, so parts of my hair remain lighter than the roots.