Here's a brief list of some of your rights and obligations. For those that don't, there is often a clear past practice that allows this. But, if not, every grievance must be investigated as thoroughly as necessary, even if it's on your own time. The boss can't stop you from getting people to wear stickers, sign petitions, carry signs, or take similar actions on break or lunch time. You should put these requests in writing.
Management is obligated to respond.
Even if a worker has taken up the grievance on their own, the boss can't bypass the union when responding. You can get loud, angry, forceful, and speak your mind during grievance meetings. All of these rights are legally guaranteed, but they depend on how well you use them. When you do, your members will find their rights are protected, too. As a UE Steward, you're elected to protect the rights of UE members and defend the contract.