I dub my modern games. You need to wait until they are mature enough that their comb is developed before dubbing, otherwise it will finish growing in all funky looking.
It takes a steady hand, certainty, and you can't hesitate half way in between. And you need a very good pair of scissors. I use surgical steel straight dubbing shears. Yes, they'll bleed. If you can keep them quiet before dubbing, that will help. I always put mine up in a shipping box deep in shavings after dubbing and place them in a dark room overnight to keep them quiet and still. By morning, they're good to go. I'll add a little Red Cell back into their water for two weeks following a dubbing to help them rebound.
But as was mentioned, there is no need to dub unless you intend on showing.