I use nice and easy because the color activator and color formula are equal amounts of liquid.
Supplies. My measuring cup is from a bottle of liquid children's Motrin. But a tablespoon will also do.
Measure out 15 ml of both liquids in small container. Mix well with plastic spoon. You can use more or less if needed just make sure you use equal amounts.
Put on gloves and use brush to apply to roots. (You can buy extra gloves from the dollar store and you can use an old toothbrush or your fingers to apply color).
Make sure you tightly close the 2 bottles when you're done mixing and put away till you need them for the next touch-up. Depending on how much you use, you'll get 3 or 4 touch-ups from 1 box.