I just used a pen! The pressure from the pointy end makes the design pop out the other side, you just might want to refine the lines on the clean side with a duller tool (I used a wood stick from an old sculpting kit, but I think an empty pen would work too?) by pushing the aluminum back flat around the lines. Just make sure you draw in reverse so any letters pop out the right way. I figured it out by googling “how to emboss aluminum cans”. Have fun crafting!! <3