Cindy, I couldn't have said it better! That is what I do as well, when I (used to) bring in another kitten. Some took 2 to 3 weeks, and no it was not necessarily the last ones to arrive, when I had a lot here. It is just quirky,and up to them.

Oh, you will need to have a water squirt bottle handy for about the time you do allow them out together, and for a few days after that. Remember, once you do have them both out, start with this only when you are home and can observe. May need to do that for a few days as well.

Sounds like you are on the right track.