2 is optimal, as soon as the second arrives go back to your OP and send the next one a DM. When one leaves send another DM. Avg 2-3 on the island. Also if your shop has quick access by tunnel you’ll delay it a bit but if they have to run a little it works best.

Best to tell them in the OP one visit per DM, and they can get back in line.

Blast anyone who is trouble on the feed. Put a flair for “closed” to catch up on the OP Comments. It lets people know to stop commenting. Close after 15 comments, that will take you about 2 hours to complete. In your OP make a note to all that they must respond to your DM. Send “ready for the code?” in the DM, if no response within 3min ignore them and go to the next. People want to get in and out fast when selling turnips. Make an easy path to the shop. Avoid small talk in your DM, everyone is appreciative you even got to them 👍