How To Catch A Tricky Horse?

Hey, about a week and a half ago i started helping with 4 Highland ponies. The owner Susan used to be a riding instructor so im helping her to back her 4 yearold gelding next month, Dragonfly. Shes pretty much assigned Dragonfly to me and i am absoultley thrilled at this but i have a slight problem. Dragonfly is an obvious pony so has a cheeky side to him but nothing i can't handle, the problem is when Susan sends me to go catch him in the feild i go up to him asking him to stand and he walks off, so like susan told me to do i follow him saying stand and after about 30 minutes he stands and i drape over the leadrope and he knows hes been caught so stands perfectly and walks pretty well too. i just feel half an hour is quite a while and people do it in minutes. its not about trust as he does it to susan too, and shes had him all his life. ive tried asking him to stand then when he walks away i turn my back on him... this doesnt work. i wondered if any one had any ideas that could help. thanks (: x