When introducing a resident dog to a new cat or kitten, we recommend letting them sniff through the door of the sanctuary room, first. Provide plenty of opportunities for them to smell each other through the door. Consider swapping bedding so they have even more of a chance to familiarize themselves with each other's scents.
When the time comes to introduce them face to face, resident dogs should be on a leash. Your new cat/kitten may hiss or growl at the dog. This is perfectly normal and should be expected. Never punish your cat/kitten for communicating his/her fear or anxiety in this way. Go slow with these interactions and end them as soon as your cat/kitten shows signs of stress. Repeat as many times as necessary after enough cool-down time has passed.
Dogs should not be allowed to chase the cat/kitten under any circumstances. Until you feel that your cat/kitten and dog are completely safe with one another, do not allow them to be together unsupervised or off-leash. It can take a month or more for them to be allowed together with no human chaperone! Make sure to bring your new cat/kitten back to their sanctuary room if they and/or the other animals in the home start to become overwhelmed.
Cat introductions can take a long time. It may be several months before your cat and new kitty warm up to each other. Do not leave them unsupervised until you are sure that they can be left together safely or until they are roughly the same size.