I'm finding it difficult to get Willoughby to walk consistently to heel for any great length of time. He is very good for short bursts with left and right turns, about face turns and fast and slow. Generally walking him on lead, he doesn't pull but tends to be a bit ahead most of the time unless I nag him a bit and then he gets back into position but soon starts to creep forward. He also walks a bit wide as Merlin prefers to walk close to me so Willoughby is on the outside when I walk them together. Anyway I can correct him?