CBJ,
There is some finesse to "feeling" the right angle. Unfortunately, there aren't many jigs out there that will help you maintain that angle. You could mabe make a wedge at the proper angle and rubber cement it to the side of your blade if you don't think you can hold it. Problem is you'll be grinding it as well. I know quarters vary and these therefore your angle will too, but keep in mind, it's just an approximation. You could also fold a piece of paper like you're making a paper airplane, then fold it the same way again and it will give you a 22.5 degree angle.
Once you establish what the angle is, It's not very difficult to keep the blade at that angle. Most people probably do it by referencing the distance of the ferrule from the top of the stone/hone. If that distance is about an inch, most people can see the difference between that inch and an inch & a half, and know whether or not they are maintaining that angle.
I hope this answers you question. Bruce may have a better response.
Marlon