Duplicate stitch is very easy to do, especially if you've ever done cross stitch or needlepoint.
I have made golf club covers many times and now only work them up in my own pattern. One other design you might try is in place of the numbers and duplicate stitch you might want to consider stripes. I really like the way they come out and you can view the stripes from all angles not just one side like the number would be. Just something for you to consider.
Wool is fine to knit these with, I just like the idea of having them be machine washable so I usually use Plymouth Encore which is a 25% wool/acrylic blend.