I went the first business day after Christmas during lunch. As you can imagine, the line was long: standard line had 3 open windows and about 10 people in line, 1 express line was open with about 5-6 people in line. I didn't know the best way to ship a return item with a prepaid label and a box that didn't fit the product well so I assumed I needed to buy a box, use the prepaid shipping label and stand in line.
An attendant advised my to just buy a roll of packaging tape ($3.30) rather than a large flat rate box ($10+). I did still have to stand in line but it moved efficiently. I was out of the post office in 7-9 minutes max. I saved money thank to his advice and was out of there quick.
I use this post office often as it's located by my office, while sometimes it can be frustrating waiting it's never unexpected or unnecessarily long. All of the attendants were friendly with everyone.