I have a tip for using digital stamps and Copic markers!
When I used the robot digi stamp, I colored over the robot eye and had a small amount of smudging. I realized that my printer laid down a lot of ink for solid parts of the digital stamp. All I had to do to eliminate this problem was rub over the more solid portions with an eraser, which removed the excess printer ink. You might not have this issue, depending on what printer you use, but just in case you have one like me (SUPER cheap ink jet), it might be a helpful tip for you. LOL