I try very hard to have a consistent program when i train dogs, training in a manner from the start that makes later training a little easier for the dog to understand, based on early cues and body language. For example, if i step sideways away from my dog, that's his cue to leave my side and go around the sheep. If i walk forward towards sheep, i expect my dog to move forward and make contact with the sheep with me. I am very consistent in these cues right from the very first sessions.
By using this consistent system, I begin teaching that blind 600 yard outrun the first time a dog is on sheep! Actually, i even start this earlier with some of my own puppies. If i'm sitting at a trial with a little pup on my lap and he notices the sheep on the field, i'm making a little sss sss noise so he starts associating that noise with sheep. I've had puppies as young as 8 weeks watching sheep at the top of the Open course, and you can bet i'm trying to take advantage of that, as well as let the pup know i like that he's looking for sheep!
I use three signals to help my dog find sheep when they are out of sight, and i begin using them immediately upon starting a dog.
I always approach the sheep with my dog by walking straight forward towards them, making a little sss sss sound with my mouth, almost like a very, very quiet version of a walk up whistle. The dog learns two things - that i walk straight towards where sheep are, and if i make that sss sss noise, sheep are directly in front of me. The dogs love that sss sss noise, because it *always* means sheep are around, where i do occasionally walk around without going towards sheep. :-) When the dog is a little further along in his training, and being sent for sheep that are a little further away (but still in sight if the dog looks for them), i'll walk forward, make my sss sss, and when i see the dog lock in on the sheep, i'll add a "there". Then when the dog is even a little further along, and being sent for sheep that are out of sight, i'll again use all of my cues, and when the dog looks in the right direction, i'll use my "there" as a way of saying "yes, you're looking at the right spot, sheep are out there right where you're looking". Over time, i need to walk forward less and less, and the dog learns that i'm facing where the sheep are, but i have that walking forward to fall back on if my dog is confused. Eventually, i can stand still, facing sheep anywhere, give my dog a little sss sss under my breath, and see the dog start scanning the field with his eyes looking for sheep. And when he faces those unseen sheep 600 yards away, i can give him a quiet "there" and he knows exactly where he should be finding the sheep on his outrun.