That is just wonderful news! And four girls! WOW!!! I had 2m and 1f just two weeks ago. I have taken tons of pics and I can't wait to see yours. I'm so glad she and of course, you, had an easy whelp. That is just great!
You asked about what to use to identify them. I have 3 daughters and have tons of hair stuff. Before they were born I found different sizes of elastic rubber bands, you know the really good ones that don't tear hair? Since I had no idea how many she would have and the most important thing - - - how big around their necks were going to be. So I found 5 of each color in three different sizes.
When they were born, I ended up being able to use the smallest on each one. Now they are on size two and I just changed out the size of the band but kept the same color. Ta Da! Anyways, you have to be SO CAREFUL to check their necks with the bands EVERY day, so they don't tighten. And believe me, they will tighten overnight as mine were gaining over an ounce a day when they were first born. And don't try to take off the bands when you are changing to the next size. Just cut it off. It's not easy to do with their heads being so little. I started to do it with the little girl and I thought "what the heck am I doing this for
!?!?" putting her through the pulling over her head and I just got the scissors. Okay, I'll quit rambling. Sorry - the rambling just happens, I can't help it.
Have a great day and I hope this helps!
Congratulations again!