Hi Little one,
I used a shield for DD1 for 7 months, she attached straight on and I found she got plenty enough milk. I regularly tried her without the shield with no joy! DD2 on the other hand attaches easily without the shield, maybe a better sucker with a lower roof on her mouth i am told. Either way as long as I could keep feeding I was happy, even though the shield is a little more work. Good luck with it.
P.S I had bleeding nipples with DD2 and they healed (although super painful at the time) within a week and all was good.