ORIGINAL: barefoot
Hold you striker a little higher than you would a pencil and Lean it a little. Push it directly away from the lean. (If you're right handed, the lean will naturally be to the right, so push the striker across the surface to the left.) Adjust the pressure so that the tip skips across the surface. Vary the pressure and your grip. Play with it a little and work it into a bit of an arch pattern. You'll be purring in no time!
Sounds like your talking about a slate pot call... Were talking about a scratch box call[:-]
For yelping and purring I very the pressure(howtight I hold thebox)on the scratch box and the pressure on the striker
Also you can play with the angle that you hold the striker
