Water Make-up works just like watercolour paint. Use the brush and a little water to soften the make-up and make it a bit pasty. Test the colour intensity on the hand. Don't work too dry, but do not use too much water.
First apply the green base and don't forget the neck and the ears. Once this layer is dry, you use a brush with black to create the shape of the scales. The scales can be highlighted, if necessary, with a lighter green colour.