Oppps, maybe if I actually read the question I'd be able to answer it better. The thread I referenced only refers to papering pre cut fins. I'm not sure it matters whether you do it before or after. I can't see any advantage either way unless you use full page labels as is mentioned in the thread I referenced. In that case you can save a lot of label pages if you do it after since you can position the fins any way you want. I can generally get low power fins covered with a half sheet of label paper and I save the rest for the next rocket. Covering the whole sheet of balsa would likely mean a full sheet per sheet of balsa.