Me and my dad and all the guys we hunt with used to "grunt" into the call. The duck calls used to be made where you needed too. But later we find out that your not really supposed too. If you can do it good then it doesnt sound too bad, but thats not how its supposed to be done anymore. And for the feed call, it would be better to say tuka tuka or tikka or anything like that, whatever works for you. Fibrating your tounge would make it go too fast, you really dont want to super fast purring type feed chuckle. Thats really for competition calling and doesnt help that much, just a few short bursts of tikka tikka tikka tikka tikka will work. Another way to think of calling, take the duck call and just blow into it, you can hear how flat and non vibrant the sound is. now hum into it while forcing air with your diaphram and you will hear it get real shaky and raspy. Now stop the air your pushing with your tounge, then let the air out like your fixing to say "two" and then force the air out while humming. make sure you use plenty of air. Hope that helps, good luck.