It's a good idea to put a little grease on the threads when you reassemble any threaded parts. In the video he was threading the bottom bracket into the bottom bracket shell. It keeps them from corroding and seizing up. Also good to put some grease on your seatpost to keep it from seizing. I always have a tube of Park Tool Polylube 1000. I use it for thread lubricant, spoke nipples, and hubs. There may be better options out there, but they have it at my lbs and it seems to work fine for me. A tube lasts me a long time. The only other lube I use (other than chain lube) is Phil Wood's tenacious oil. I drip some of that into my freewheel body after cleaning it.