First thing about powder is be real careful while mixing it, pyro is a toxic chemical, second if you do mix it use distilled water, pyro usually lasts a very long time even in liquid form. The times for pmk are available at digital trugh website. Usually it is recomended using non alkaline fixer, and water instead of the stop bath in order to maximize the stain, you also might want to put film back in the used developer after you fix it, again to improve the stain.