I've just been using the brush that comes with the powder pal to brush the EP off the tray. Then I rinse it under water. Sometimes I use a little dishwashing soap. When I first started embossing, I accidentally got some of my silver EP into my black EP bottle. BIG mistake. Now I'm super careful not to leave any EP on the tray.
I'll have to try the tip about the embossing buddy on the tray.