L.B.
I've nursed two kids 21 months apart, now 3.5 and 22 months. I own one nursing shirt that I found at a second hand store, but I didn't end up using it very much. Though I didn't do any tandem nursing in public, I never had a problem with just lifting my regular shirt. I did use a sling to hold the infant when I could. Sometimes I would cover the baby's head, but that was rare. I didn't feel like I was having to show much boob to get the baby latched. I still nurse in public and don't give it a second thought.
Good luck.