I have two neutered male cats approx 6 years of age. A few days ago I took on a female neutered rescue cat approx 4 years. So far, she has been confined to a small bedroom most of the time. A couple of times each day I have been shutting boy cats away and giving girl cat the run of the rest of the house.
She seems fairly ok in herself - eating quite well and using her litter tray and playing with toys. The cats have seen each other a couple of times through a glass door. Boy cats are very curious but no hissing. Girl cat hisses a lot.
I am using Beaphar cat comfort calming diffusers. Not sure how to move on from this point. Any pointers appreciated.