How do you re-introduce separated frogs?

[cornelius]

I have two panamanian giant auratus dart frog juveniles (the green and black kind). Both are about one year old, but one is getting quite a bit larger than the other. The smaller one is a lot shyer of an eater, so I separated the two of them with a tank separating screen.
Once the smaller one gets larger, I would like to re-introduce them and take the screen out. How should I go about doing this? Should I do it little by little, or can I take it out and leave it out?
If anyone has any advise, I would really appreciate it. Thanks!