Trouble with latching

My twins were born at 33 weeks. While they were in the NICU they initially had feeding tubes, then switched to bottle feeding. Breast feeding was out of the question for the first few weeks. We started trying to breast feed at 3/4 weeks. But they were extremely nipple confused. We switched bottles and that helped some. Right now they can only feed with the nipple sheild. I'm afraid I've been using it for too long. They are 6 weeks old now. I need to try to wean them off of the sheild. Does anyone have any experience with his or advice? Techniques to maybe make it easier for them to latch?