Scratching in the leaves is about as good a close call as you can use to coax a bird those last few yds and you can do it with one hand while you hold your gun up with your other hand. But if you just hafta know how to purr try this. First- practice without a call at first. place your tongue against the roof of your mouth, bring air up from your diaphram (the key to purring), keep your lips closed loosely, now flutter the tip of your tongue against the roof of your mouth. I feel like I create a hollow air chamber in the rear of my mouth as I do it. You have to get this action down before you introduce a call into the picture. Once you do add a call. I make calls and my best purr calls have significantly less stretch and as far a purring calls go less is "usually" better with two reeded calls "usually" being easier to purr on. I have good luck with split V, batwing, modified batwing and ghost cuts and really feel its more about the stretch than it is the cut. Once you learn to purr like this you'll be able to add little whistle's, cluck's, etc. to add to the realism but keep scratching the leaves. That's the real killer. Good Luck!!
Dan