I know that you have seen youtube videos, but would recommend having a look at this thread. It helped me no end when I was trying to work out how to hold the wrist flat and the elbow above the strop. It may also help on angles. The second is the wiki article with info on angles and a couple of good animations. I would probably read the second article then go and watch it in practice in the videos. The videos are great since there are good comments after each!

http://straightrazorpalace.com/strop...st-2012-a.html

Razor stropping - Straight Razor Place Wiki