1) In the beginning when the doors open, don't be scared just go to the cart, all you do is push the cart on pl so it doesn't matter if you die. If you die to stickies you clear the way for more important people.
2) Don't just sit around and push side flanks that are cluster fucks. If it looks like you'll get mulched by a soldier you probably will. (top left @ 1st point). ALWAYS BE DOING SOMETHING and that means pressuring cart not tagging the heavy being healed for 15 dmg
3) Don't bait your team on the cart, your job is to push the cart not the other way around, just back on and off the cart so they can't ignore you, but if they put too many people on you, you're free to run away.
4) DM, your aim will get better with time and practice. Dm/mge or just keep playing
5) Milk honestly isn't that important. I'll probably run pistol 3/4 of the time.
6) Communicate with your team instead of just talking to your stream. I know you're streaming but the team needs to know what you see instead of just reassuring yourself that you're the MILKMAN.