How long should I let them 'establish dominance?' Because about four seconds in I freak out and pull them apart.

I'm trying to get my two pairs in the same cage as a quad, and the only thing I successfully did this time around was scare myself, my gliders, and cover my tent in poo.

Any help would be greatly appreciated.

Are you able to just wave a piece of fleece or something near them to break them apart? Sometimes, they'll need to have a few times of making noise and rolling around. I think you're right in letting it last only for a few seconds...then just wave the fleece and let them go about their business. If they continue this, though, I would only work on intros for maybe 20 minutes or so at a time so they don't get too upset.

No, it's not quite that easy to get them apart, but they do separate if I stick a finger between them. I am sort of worried that it's a serious fight, but there isn't much crabbing so...?

There probably won't be crabbing - they make a totally different sound when they fight. IF they don't separate easily when you wave a piece of fleece or make a sound, then it's more than just "wrestling" and my feeling is that it's time to back off a bit and work more on swapping pouches and toys.

Alright. This is the first time I've tried introductions in some times, so, that's why I had to ask.

Always better to ask. When I did intros with Penny (intro'd her to my trio), they did wrestle a bit, but they would separate quickly when I waved a piece of fleece or made a noise. If they aren't...things could turn in an instant. Just watch for that.