Ok so I've been using it for a few months now and here is what I've found. I've been using Brow Henna by irina levchuk.
It reacts fine so far with my clients who I usually use regular plant based tint on..refectocil etc
The darker shades are easier to work with and cooler toned whereas the blonde shades are very warm and I haven't found the right mix yet. I'm almost ready to write the blonde shades off completely.
I don't find it lasts more than a week on the skin unless using the darker shades.
There's lots of professionals on instagram using it but usually in the middle east so I can't read what blends they are using
any western countries using it don't provide regular updates so I suspect they have the same problems.
When I do get color combos right on the right client it can be magical so I'm determined to figure it out.
It's very expensive
Personally I'm not willing to take the 300$ training plus spend so much on the product but you basically take the powder and mix it with water so it should be straight forward.