I love it!

I had about 60 percent grey / 40 percent ash blond-mousey blonde in the front and 50/50 in the back.

I used henna from mehandi.com, and a mildly acidic kitchen mix with lemon juice. I left it on for about 4 hours. The color, texture and shine is just amazing!!!! Love it!!!

Notes and References
Henna: https://www.mehandi.com/Mehandi-com-Ancient-Sunrise-Henna-for-Hair-s/121.htm
Don’t have fruit juice on hand? Keep some fruit acid powders in your cupboard.
Mildly acidic liquid: https://www.mehandi.com/Fruit-Acid-for-henna-dye-release-s/299.htm
More info on mildly acidic mixes: https://www.tapdancinglizard.com/henna-and-acidic-mixes/

Video How-To
Going red with henna: https://vimeo.com/manage/videos/739464950