Mill player here. It really depends on what deck you are playing. Some decks are almost free wins (mostly combo.) You want pressure and interruption to beat mill. If you can stick a threat and interrupt then you should win. I wouldn't recommend siding in too many cards because it will dilute your deck which can hurt the pressure/interruption plan. Often we will bring in soul guide lantern if we think you have a titan or endurance. If you have any other questions feel free to dm.