The right way is to have them mentor with someone even if that slows down the mentor (and it will). Don't assign them to a curmudgeon either. If you don't have the "manpower" then just let them have a couple of months to adjust (assuming they're really hired on and not a consultant) and take it all in, they're already stressed and tacking on a thousand (paper cuts) points of improvement is going to make them feel awful.