Can't specifically answer your question about packaging but suggest you make a note of the details (model, serial no. etc.) of all kit that you are returning. Also note date and time the items are collected and some identifying details of the person who collects (van reg. no., staff badge ID no. etc.)
Some past topics have described long delays between equipment being picked up in this way and finally checked back in with VM, resulting in the customer continuing to receive unstoppable text reminders for the equipment (even though it has been collected).