Introducing a new cat to an existing cat
So, because of some advice from a previous post about my very independent (1 year old and female) cat, I (or should I say my husband and I) decided to get another cat (young cat). We found a very longing a playful female cat that we fell in love with (she's 9 months old). We have set her up with a safe room down stairs and plugged in feliway (vet recommended it). She's been down there for over a week now. They have played with paws under the door and have gotten used to each others scents. They have seen each a couple of times face to face, but here's what happens. The existing cat comes into the room and our new cat purrs and tries rubbing against her. The existing cat sniffs her, and even grooms her a little and there really isn't any aggressive behavior. As soon as the new cat leaves the room, the existing cat runs in front of her, put's her paw up and will smack her, and chase her, and be aggressive even if she goes back into the safe room, so we end up separating them again to start over.. I know the existing cat is protecting her territory, and we have to be patient. We also will make sure they have separate feeding areas and several litter boxes in open spaces when the new cat gets further than the safe room door.
I've heard of putting the new cat in a carrier so the existing cat can see and smell, but the new cat is still safe and not stressed, I just don't really know where to go from there if that is the right way..
How exactly should we go about advancing this so the existing cat won't fell like this is a huge invasion of territory, and the new cat won't get so stressed from being punished?