Progress is shared for all but Urgent Quests. Even across ranks.
Our team yesterday had some of HR2 guys and they still had credit for the HR3 quests we did before we helped with their urgents.
As for general advice: Be mindful of your weapon against teammates . (Hammer smash, Switch Axe upswings, etc)
Don't just rush for the head when you're better suited for more general areas as opposed to stunning or tail cutting.
Some other helpful info:
- You don't need to leave online to change equipment, you are free to head to your house whilst still being online.
- Meal vouchers are shared, so everything should be fresh for everyone is someone uses one.