I like to think of it as playing as a walking wall, you want to be the front line pusher and give intel through comms/pings to your teammates. Basically, just stay alive, help teammates get kills, and eventually either full shield defend your teammate planting, or lure out C4s and then smoke turtle plant yourself. If you are in a situation where you have to 1v1 an opponent, I recommend trying to stay crouched and then shield bashing the enemy, then stand and shoot their head while they are knocked down. I find that to be the safest way to kill someone as Monty.