One of my two, 6 year old Louis, is reactive towards other dogs. He's worse on lead than off, but of course there are times when I have to put him on lead even though I know he's more likely to react.
I've had a lot of success with LAT (look at that) and if you do an internet search for it you'll find a much better explanation than I can give. Basically when Louis sees a dog, even if it's a long way off, I try to capture that moment that he looks at the dog and say "look at that" in an encouraging sort of voice and reward him for even the smallest calm reaction. A casual glance, looking without immediately putting his hackles up, anything positive gets rewarded.
If it's a close or sudden encounter and he reacts by lunging or growling I simply walk away with him calmly while calling out an apology to the other dog owner. I can't let myself get uptight about it because that just makes Louis more anxious and more reactive. If I see a dog approaching that I'm pretty sure he will react to I turn and walk in a different direction if possible.
It's worked really well with Louis. I know he'll never be perfect around other dogs but he's more confident and can now be a lot closer to other dogs without getting worried and reactive. He can look, think and stay calm instead of looking and immediately reacting.
Could you try the same tactic with Fraser? You're already scanning for other dogs so while doing that watch Fraser and the split second he sees the other dog say "look at that" and reward him. I think if I was you I'd also not let him greet other dogs while he's on lead for the time being, simply to take the pressure off him. He has doggy company while at doggie daycare so it's not like he has no other interactions with dogs. Stick with those positive ones for now and try to avoid the negative ones?
