It's quite easy. You spray the base coat-in my case alclad-you let dry,then hairspray,not directly but using an airbrush,you let it dry,then the color you want to chip-in my case Gunze green-and when everything is dry, you use a not very soft brush and with a little water you start brushing the green-or whatever-until the alclad is starting to show..
HTH,
Panagiotis.