I have been fascinated by impressioning so naturally I had to give it a try. With several failed attempts, I realized I needed to set myself up for success if I wanted to learn this skill so I made a blank holder and bought a swiss 4 cut file. That was about 6 a year ago and I have been enjoying this skill ever since. Here is a pic of the blank holder I made with the 3rd ever key I impressioned (I have since purchased a commercial holder) and a key I impressioned last night. You can notice how the cuts have improved over the time/practice.
http://i.imgur.com/urJMgjz.jpg
http://i.imgur.com/qluXHsH.jpg
This USN Yale is actually mine. I mention that because out of all the locks I impressioned, 80% of them are Jeff Moss' locks lol so its nice to work on a lock that is actually mine haha