Has anyone ever painted on buttercream before? I need a wood grain look on a guitar cake and the person wants buttercream. How do I get that wood grain look w/ buttercream? I was thinking painting over the buttercream with colored piping gel???

I have never seen it, but Martha Stewart frequently makes crafts and recipes using a 'woodgrain rocker' - it imitates the look of wood. You may have to look into it further, but I think if you used that over your buttercream it would leave the design in it. If you wanted the woodgrain to be a different colour, I believe you could roll it through the colour of buttercream and then apply it your buttercreamed cake....