I'm doing my first bag sale right now, and even I managed to add a BIN after a couple of days, so it's definitely easy & do-able. The one thing I would caution is make sure you watch for it if they add one and actually use it. I had several people ask if I'd add one, so I did, but it sat there for 3-4 days. Then after someone placed a bid (and the BIN therefore went away), someone emailed and said "oh no, where did the BIN go? I wanted to buy it outright. Could you relist with BIN?" Again, it had been there for 3-4 days with no takers, so I really didn't want to cancel the bid and relist!! So, if you ask for BIN and want BIN, be sure to actually BIN when it gets added or you may miss your chance.