Same as Stretch. The two magic elements; light strokes and match the angle. I suppose there may be other ways, but this is the only way that ever worked for me.
You can find the correct angle by moving the blade in the edge forward direction very carefully as you slowly raise the spine. When the edge first starts to bite, that is the correct angle for stropping. You can repeat this guide step over and over to set up each series of strokes. Also, if you are realy good you can feel when you are stropping at the right angle. The blade feels like it's floating across the strop without any raspy feedback. Using this precise angle seems to be very important. Also, if you use pressure the compressed leather will spring back from under the trailing edge and round it off resulting in a very smooth and dull edge.
(By the way, I'm not sure this advice is accurate for a convexed edge.)