Recording/taking pictures of management people working is a great way to make sure you're looking for another job if you're in a UPS facility.
All you need are witnesses to volunteer. Typically, listing at least two witnesses is enough for an Article 3.7. If the company doesn't want to settle it with the steward or with the BA at a local level, then you'll need written (and notarized) statements from all witnesses. Notarized statements from witnesses on the record are going to be a hundred times more effective than 30 seconds of low quality iPhone footage.