You said you had buddies that hunted. Try whatever calls they have and see what you like, everyone is different. You said you can feed call... the only time ducks do the rolling/ machine gun chatter is when they are flying. It sounds really cool, but not very realistic for feeding ducks. When they feed it is very broken up with quacks mixed in. Learn single quacks and 3-5 note calls, that will kill ducks. Call at tips and tails is a good rule, if they are committed and coming in don’t blow them out. Youtube videos of real ducks are good, and if you can find some real ducks to go listen too you can learn a lot.