I can't seem to push enough air over the call while making the gurgling to make a soundIt's hard to explain how to do anything with a mouth call. The best I can offer is that purring (for me) has almost nothing to do with the tongue. It's from the throat. Like you're trying to replicate the sound a cat makes when it purrs or the gurgling sound of a sandhill crane.
Try a call with very soft reeds, experiment with different cuts until you find one that works for youI can't seem to push enough air over the call while making the gurgling to make a sound