Wes,

Good clay or bentonite should be incorporated into the top six inches of existing material with a disk, rototiller or other implement and not just spread onto the soil surface. Recommended quantities vary with existing soil conditions. Probably 2 to 3 pounds of good bentonite per sq. ft. should do the trick. Doesn't sound like much until you do the math for a surface acre..... 43 to 65 tons per acre!! This can get expensive in a hurry unless you have some other good clay material on hand.
Good luck,

Ed