Cat Flap/Pet Door

I just purchased this CAT DOOR. I plan to put it into my back door, to allow the girls out in the sunroom (only when I'm home and awake!) I've been leaving the back door open a crack to allow them to go out unrestricted, but I know I'm losing a lot of air conditioning through the open door. With the high price of utilities, I imagine that I will recoup the cost fairly quickly.

I'm sure everyone knows how timid Maggie is. She's terrified of her own shadow! I really expect Cleo and Lola to learn to use it in no time, but I'm worried about how Maggie will react. I have Feliway spray, which I think I will spray around the flap. I will also leave it completely open for a while, so everyone will be able to get used to it.

Does anyone else here use a cat flap for their cats? If so, how long did it take them to get used to it? Any tricks for training the timid ones?

That's similar to ours -- different brand, same features. Our experience is that it takes about one afternoon of intermittent helping and leaving alone for them to get the idea and be comfortable using it. Starting with a human on each side and treats to encourage them helps, as does holding the flap wide open the first couple of times and then gradually decreasing the opening to the point where they have to break the seal themselves. Teaching more than one at a time is fine, as they seem to learn from each other that it's OK, even if it is weird. Good luck!