I used Woodland Scenics snow for this dio. Used with their snow adhesive. Got them at Hobby Lobby.Used white floor tile cement to build up pile then added the W. S. snow on top. This was my first ever dio. The snow was very easy to work with.
Here is what I do for whitewalls. You will need a circle template with various sizes on it and a white Sharpie marking pen. Find the size you want and place that circle on the tire and fill in whitewall with the white Sharpie. The Sharpie dries a bit flat similar to whiteout and looks fairly good I thought. No sprays and little mess!