Hi all. I'd like suggestions on the best way to re-introduce my 2 Gouldians. After having them only a few days, I had to separate them for fear one was beginning to Stargaze/Twirl. Thankfully, he seems to be doing fine now and hasn't exhibited any abnormal behavior in over a week

I'm ready to put the 2 together once again (both males). They have been living alone for about 3 weeks in separate rooms. I'm worried about how they will accept each other since they both seem rather happy singing to the mirror in each of their cages (I put mirrors in so they wouldn't be lonely). What would be the best way to bring them back together? Do I just go for it all at once? Should I put the cages side-by-side for awhile? What should I watch for in terms of aggression to indicate the need to separate them again?
Thanks in advance for your advice.