Don't wave it around, work it in a slow smooth line. You'll have to experiment with getting the nozzle closer or further from the dog to prevent the whip-knots. The distance you hold the dryer from the hair will make a difference to the tangling. It helps when doing the feathering to blow them straight down until you get the technique 
I us it on my clipped pair and the show pair.... I try to dry in the direction of the hair. Could also be used with a dry coat I guess
Thank you both, I appreciate that, I will be trying to get to grips with it this autumn and winter, thanks again
