I am not CG as that doesn't work on my hair. It gets limp and greasy and isn't any more curly than if I use a very moisturising shampoo and conditioner. If CG is working for you then maybe you just need a more moisturising conditioner after you colour. I like Tresemme naturals which is silicone free.
I am mid forties and have very dark hair with a sprinkling of gray so I need to color my roots, too. I used henna for years, then decided to switch back to chemical color so I could do highlights, and I hated the experience. The chemical color lightened all my hair and made it red and coarse. I figured if my hair is going to be red anyway I might as well go healthy and use henna
Also, certain chemicals in dark brown color have proven to be dangerously allergenic, and my last "patch test" made me red and itchy and scared me off for good, so I'm going to stick with henna from now on.
I use henna and indigo from Henna for Hair. I leave the henna on for 3 hours and the indigo for about 1 hour (still experimenting with this). This gives me a really nice dark ash brown with very little red, and it seems to hold up well for several weeks before the indigo fades (the henna never really fades, so the gray doesn't come back). It is much more expensive than box color and takes WAAAY longer so this may well not be for you, but you did ask what other people do!
After I henna I rinse with tons of conditioner (this helps to get the henna out of the hair) then pile on coconut oil and let that sink in for as long as possible (ie overnight). Then my hair is colored and shiny when I wash and condition again.