It's awesome that you decided to take in the little one!
I had a cat before and I succeeded at teaching her to stop whatever she's doing at a special hissing sound... This I used to teach her to stay off the kitchen table and to stay away from scratching the furniture. Never had to yell or hit her once. Just the hissing that told her she was doing something wrong. Well, and a lot of love and patience that went into teaching it to her
