I usually start with a one high, shrill note that rolls off. It's basically the "you all" part but with more excitement and a higher pitch to start. After a couple of those I do the standard "who cooks..." and then if all else fails, I'll go into some laughs that roll into that high first note again.
Not sure the Walmart call is the reason you aren't getting gobbles, but the Hook's owl call is hard to beat. It sounds so awesome and is really fun to work. If you're not getting gobbles with that, you won't be blaming the call, that's for sure.
Sometimes they just don't respond to the owl. Over the years, I've gotten tons more owls to respond than I have gobblers. A lot of times, when I'm trying to roost one in the evening, I'll follow the owl up with a crow call and sometimes a box call as a last resort. I know a coyote howler would work too, but I just can't get over the weirdness of making a bird gobble with a sound of something that would be trying to eat it.
Good Luck!
