For my test, I used yellow copy paper. I would not suggest that you use copy paper or thin background paper. The embossing actually cuts into the paper making it difficult to trim the paper after it's embossed.
The brayer technique worked great. I found you need two things for this technique to be successful. A folder with busy design If you use a folder with a lot of raised area this technique works best. Two, a light touch when brayering. I reinked my brayer a few times to get good coverage because I didn't want to apply pressure when brayering. The light touch keeps the ink out of the areas that are not embossed.