Introducing foster cat to resident cats

I have agreed to foster a 15-year old declawed spayed female cat. She is good with humans and dogs, but has no experience being around other cats. My resident cats are 3 females (15, 11, 10) and 2 males (3 and 2 years), all fixed and all have claws.

If any of you have experience with successfully (ie, calmly) introducing a cat such as this to your resident cats, please relate what worked and what didn't. So far I'm keeping Chelsea in a spare bedroom with her own food and litterbox, and only letting her out for very brief periods (while my cats are shut in the master bedroom). Given her age and lack of experience with other cats, I'm trying to keep her stress level to a bare minimum. Any advice would be greatly appreciated.

Carla
slave to Hazel, Lizzie, Esther, Elliott, and Boudreaux