Dog dye

Hi! I’m a professional groomer but I haven’t worked with dye in a while. I have a client with a gray schnauzer. The client requested rainbow colors. I would like to use stenciling on her back because I’m not an artist. I also would like to do stripes on one ear and up one leg. I would like to use opawz, but I don’t think I can use the semi permanent on the gray coat. Can anyone help me out with product ideas? Ty!!