Others will probably post with better ideas and more experience but here's what we do. Ignore anything you don't like or agree with, it's just one idea. Good luck.
We use a harness on a line. The dogs have learnt that when the harness is on, we are teaching them something, so even without a line, they seem to be keen to learn and behave, because they are in training mode.
(We have two types of harnesses, one for walks and a 'indoor' harness, it's made of cloth, so soft and a bit looser, we only use it for training at home/garden) They know when the indoor harness comes out, that we want something from them. Make it positive, no negative training.
If we need to get to the dog quickly...say to teach stay with the front door open, we'd have a line attached to us. But for something like this, we'd probably put on a short line, that makes it easy for us to grab, so we can correct behaviour without touching the dog. Short enough it doesn't get caught around chair legs etc. Our short line was about 7" long (never leave on unsupervised)
Caleb is overly attached to me. He'd bark at Ishmael (border collie) or the cat if they approached, but was ok with Pip sitting on my lap. When he growled, I'd put him on the ground, make him sit (praise him for that,even though it's an easy command) and then ask Ish to approach, correcting Caleb if needed. Rewarding with praise or treats. Repeating, until he got it right. No negative corrections. Both dogs receiving praise.
It might not be a quick fix but he can't ever be allowed to growl without correction. I'd ditch the spray bottle and anything negative. Give him a set of commands, ie sit, stay, down, leave, and loads of praise, then call the other pet and have them do the same commands. You can even stand on a line or have someone else hold it. Having training sessions, after a good play or walk, will often be easier than if he's full of energy.
Walking the dogs together helps also. The dog you've decided is top dog, always gets treats first, goes through the door before other dogs, (not before us.) When training, that dogs goes first. The dogs have a pecking order, we decided it and stick to it. We noticed any time someone changes the order by accident, it causes friction in the group.
__________________ Caleb   Pippi |