I should be more clear.
Practice making the cuts and tying the unions, even if what you are practicing on is not a variety you are trying to add to your collection. Just get the reps in so that come spring when you want to make your real grafts you are comfortable with your knife (or blade) and can secure the union properly.
I remember my first few attempts at grafting, I had a nice new sharp grafting nice but my cuts left a lot to be desired. With some practice, sometimes just on pruned branches, I got much better at making good clean cuts with fewer strokes. I got a feel for how the knife handled and when it was time to sharpen the blade. In time, I gained confidence and my success rate went up.
My suggestion to PJ is to get some practice in, and out of the way, before he does it for real in spring.