Lush Henna - Anyon done this without destroying the bathroom?

[AprilSeptember]

Ok. My thin, fragile hair has had enough. I have gone full-hippy (as DH calls it) and bought a block of Caca Rouge from Lush.

I like this more now I have found out it literally means "red shit"

After watching every single video I can find, I am excited to be a flame-haired Merida type, but less excited at the UNHOLY MESS everyone seems to make.

I am thinking, as I have chin-length baby-fine hair, can I do this upside-down over the bath to avoid destroying my bathroom? If I fill a bowl and then just sort of dunk and scrub until it's all in? We're about to put the house on the market so if I can avoid dying the bathroom orange, that would be ideal.

Or is newspaper/a tarp/the garden my only option?

Help!

Both the lush stuff and pure henna are permanent. Both grow out rather than wash out. Lush henna has additives that weaken it [there is less henna in it] so the colour is not as intense. Henna is an intense red. The lush stuff is crap colour wise in comparison. It does however condition hair beautifully because of the oils in it although I find the smell annoys when I have rinsed it out.
I have mostly grey hair now and I have found that the lush henna or indigo [the brun stuff] was just not enough and ended up either with orange roots or a kind of green root thing going on. It was annoying. Henna/indigo is great for me personally as it turns out a lovely dark conker colour with flashes of firey red where my hair has naturally light bits in - the grey most likel!!!

Am using the caca brun.
I've read that it lasts longer if you do it again a week
after the first application.
It covers my greys for a while
Usually then wears off.
Makes my hair a lovely shiny texture. SO much nicer than hair dye.
My hair is a very dark brown & the caca brun makes it a rich brown no orange or green here.
Love it