I just did that yesterday at an adult class. They had a ball with it. Not sure I do it right, but it worked.
I use glossy, put the colors all over with either brayer or sponge daubers, allow to dry, then versa mark and clear embossing powder, heat embossing powder, then foam brayer entire page with black or dark blue, let dry, wipe over embossed areas with a paper towel!
The dark blue let our "dots" show through a little and it was really cool looking. The black covers every thing but the embossing.
Hope that helps!
Denice
I have a real "stampatude" how about you?
http://www.denicestampatude.stampinup.net