Don't know whether hand signals/body language alone would work with Milo given his speed though. Be interested to know what experienced agility-ers think....
No harm in using your voice as well*, just to be aware of your non verbal signals is a huge advantage. You could find in time that you don't need to keep up with Milo to direct him, many handlers with turbo dogs do it from afar. It's interesting to watch other handlers and see what they do, some hardly move from the middle of the course.
I'm going on about body language but with those still introducing their dogs to the equipment it probably won't apply just yet. When your dog is confidently running on is when you're really going to reap the benefits.
* if you can limit your voice to when you really need to attract his attention it will be a more effective tool. (edited to add this!)
There's no way I'll be able to keep up with Milo when he's reliably running full courses. At the moment I get away with it 'cos the series of obstacles we do in a course are in a fairly structured order, and fortunately I can leave him in a wait and walk as far as the straight part of course takes me and call him from there, the problem starts when I've fallen behind and am trying to instruct him when he's way ahead. I'm sure it will come in time and as he gets more confident.
Discovered this morning that Milo doesn't actually pay much attention to my hand signals and does what he thinks he should be doing, which is normally the obvious route to take.
This morning we had jump, then rigid tunnel (in a "u" shape) and then another jump. The aim was to put the dog over the 1st jump, through the tunnel and then once they were in the tunnel, leg it to between the two jumps with our backs to the tunnel and then with the appropriate hand indicate left or right, depending on what jump we were aiming to do. Milo did the jump, tunnel and left jump fine, 'cos the left jump was the one directly in front of the exit of the tunnel. But, when we had to do the right hand jump, he repeatedly jumped the left one because it was the most obvious to him and he paid no attention to what my hands were doing at all.
So, we're now going for using non verbal commands as little as possible for the next few weeks, to see if he pays more attention to my hands.