I have been thinking of hennaing my hair for a long time and now i finally did it. I used:

100 grams of Ancient Sunrise henna from mehandi.com and a mildly acidic liquid mix

I mixed all the ingredients together and let it sit for about 20 hours. Then I got it into my hair, wrapped it and left it on for about 3 hours, then rinsed it out. Surprisingly, there was almost no mess and no stains anywhere. I am very happy with the result, my hair now looks healthier and falls out less.

Thanks for your useful information about henna!

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/
Ancient Sunrise henna for hair kits with everything included: https://www.mehandi.com/Mehandi-com-Ancient-Sunrise-Henna-for-Hair-Kits-s/124.htm

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