Lunging and pulling...sounds so familiar Patience patience patience. I use the spook harness on Iker because I'm afraid that he will back out of a regular harness. Have you seen the special leashes offered by Anne Green? They attach to a collar and the harness. I tried using that with Iker at first but had better control just using the spook harness with q sturdy leash and carambient for extra security. I've also realized that I will probably never be able to walk Iker anyplace where there are people, etc. because he is simply too nervous and freaked out. Another thing that helps is if you can find a group of friends with dogs and take all have a big group walk. That will help your dog relax.
With my guys, their reactions to squirrels and bunnies has faded a bit over time, but Xavi is still very keen. He's great on a leash until he sees a squirrel or a bunny. I wrap his leash around my hand several times and try to be retroactive by trying to spot animals before he does. I try to distract him best I can, but I have to depend on muscle more than anything.
Be patient and keep remindIing yourself that these are hunting dogs and possibly street dogs who look at the world differently than you and your greyhounds do. Patience and humour .