I've recently started clicker training and you do need to be speedy. Before that, I used to say 'yes' in a quite distinctive way: quick, sharp, low, and with an extended ssss. And then treat. I still do it, out of habit and he immediately looks for his reward.
With four of us in the house, we agree all cues and commands so they are consistent. Discovered that not everyone can do that 'trot on' click! We have two people that can whistle and click, one who can whistle but not click and one who can do neither!