One of the breast feeding experts in NICU told me to rub my nipple into the bit above ds's mouth but below his nose, that made him open his mouth and you could just drop your nipple into it.
Second the lansinoh too. Find a position that works for you, I was told to use the rugby hold because of my emcs and I hated it. What worked best for us was sticking a muslin cloth under my breast and just going for the usual angle.
As for cannulas, ds had several (he kept pulling them out) and I felt dreadful but on observing him, he was fine with them going in but got really upset when he pulled them out so I think the latter must have hurt a lot more than the former.
If he's in NICU, I found they had far better breastfeeding support and more time to give it than the postnatal ward.