How interesting. We had a very protracted period of getting the dog used to our resident cat starting with weeks of them having to be segregated completely as the dog was obsessed with her and at one point had her in his jaws.
A bottle with stones was recommended, but Gymdog is not great with unexpected noise as it makes him hyper and barky - ie very similar to his behaviour around the cat - so I rejected that. We needed calm, not more chaos so I also rejected splashing water at him etc.
As ever, food was our friend. We progressed very slowly to Gymdog being able to be in the same room as the cat with her out of reach but he was still fixated, drooling, glazed eyes, legs quivering etc. Our big breakthrough happened by accident - I put a bowl of vile delicious smelling cat food in the same room but out of Gymdog's reach and away from the cat. Suddenly having two powerful stimuli in the same room, but in two different places, broke the fixation. Up until this point, so great was the fixation I could tuck a treat under his lip and he would not register it was there. With the fixation broken, he became responsive and I could work with him. I spent boxing day sat between cat and dog alternately feeding them bits of turkey and praising Gymdog for taking turns and eating turkey rather than cat.
So, distraction and positive reinforcement but not because of a conscious choice on my part between two models, but because that's what worked! Which is the best recommendation I guess. The majority of dog owners are unlikely to read up extensively on the different approaches, they just want techniques that work.