Make some very dark hot tea or coffee and add it to the powder until the mixture is slightly runnier than the consistency of toothpaste. Mix in a tiny bit of oil. And the mehndi / henna paste is ready.

To apply mehndi / henna paste, the best thing is, use your imagination. There are a no. of ways to apply mehndi / henna. Some of them are, with the help of toothpicks, knitting needles, paint brushes, etc. But the best and most popular way is to use cones. You can even apply mehndi /henna with the help of stencils which are available in the market.