When we get a baby who tucks in loser lip, we try having mom bring baby's bottom up under opposite breast using a firm foam pillow (so it doesn't collapse during the nursing session) lift and support breast with the side of the hand or use a sling, touch the baby's chin to the breast and use the lower areola/breast to roll down the lower lip right before "sneaking in" the nipple. Mom then quickly pulls in on baby's shoulders to keep the chin pressed in tight. If the lower lip rolls in, mom or helper pulls out the lower lip and pulls baby in tighter. We try NOT to take the baby off the breast too much unless mom's nipple starts hurting because everybody gets too frustrated. If mom puts her feet up on a small stool, the lap helps to support the pillow which keeps the baby supported. Also use a folded towel or blanket to wedge in mom's wrist to keep baby supported at breast level. When moms are holding babies in tightly, their muscles can get tired so firm support that doesn't collapse is important in maintaining a position. I often find that after a few days to a week, everything gets easier.