You'd need lots of water because it gets kind of flaky but with honey added just before application on hair it helps it wash off with ease, I remember when I used henna and I almost died from broken arms and waist LOL. I always do these things myself because most stylists are ignorant. You won't notice color immediately, it takes about a week depending on hair type but you'd get a reddish glow in the sun and light.
If you want to dye hair in color order than red then henna isn't for you because red/black is the only color it produces. But just before you use that permanent dye then first test hair with semi-permanent dyes to see how your hair will fair before you apply the permanent. It's important to always keep hair moisturized and leave in conditioners are your best bet. Cantu is great but I use dark and lovely.