My newest glider has been in a cage next to the others for a few weeks. He was neutered recently and his scent is pretty much the same strength as theirs now. I switched their pouches yesterday and they don't seem to mind. They do say hi to each other through the cage sides and seem friendly. When should I try intros and how should I go about it? I know they should be one on one and I was thinking of bathtub introing the less dominant of the pair with him first, but how/when should I intro the third if they do well together?

We would have 2 sleeping pouches in each cage. We notice when we switched one pouch per cage the gliders would sleep in the one scented with the gliders in the other cage. This was a 4 colony in one cage and a single in another. We never had the cages together on this last intro. but they were in the last room.
My wife would put the single glider in the tub, then add one from the 4 colony. We had a clean unscented cage setup. then she would add another, then another. Let them all get a sniff in, push away any big spats (didn't have any this time.) after about 15 to 20 minutes they were all good and ready to go in the new cage while we were home and in the room...the first night we keep a close eye on them that is when being awake and alert they could change their minds on having a new guy/girl.

The quickest we have done intros is after 2 weeks of cage closeness and pouch swapping, but I prefer 4 weeks. The big thing is to carefully watch in tub, let them sniff, let them even tsk or spat some (this is the part my wife does well, while I freak out.) BUT if they ball up and are NOT making noise, cause they are to busy biting, that is when you have to be ready to stick your hands in tub and separate. For a big spat we let them still go, but if 2 or 3 big ones, we will stop introductions and try another day... I don't think it is bad at all to stop a BAD intro, just have to be sure that is what it is and not just a spat.

We got rescue of 2 and 1, the owner said they were unsuccessful with intro cause in cage one would chase another. The single seemed to really need friends, so in 2 weeks we intro, they had been living next to each other already for a long time. The one female would chase the other female WHILE eating, when she got in her face trying to steal food. we gave them 2 feeding stations and after a few weeks of a few chasing because of the food, they figured it out and were fine. It also helped the single be so much less nervous and be a nice sweet glider, much more calm.

Introed them last night, submissive one first, they immediately snuggled in the pouch, added the dom and he immediately started rubbing his chin and chest glands on the new guy. Slept by their cage last night and no fighting, just the usually disagreements. All 3 seem a lot more happy to be together, I think the other 2 were pining for him a bit as well, they always wanted to go to him.