I have been given permission to repost this advice/experiences from a rescue which offers residential boar dating over the course of a week, with a great record of success... It might help
Boar dating checklist.
I let the pigs meet on the sofa, either side of my lap to start so they can see each other and get to know each other a little, 15 mins is enough - if they do not want to kill each other at this stage I move them in to the bonding pen, once they move to the bonding pen I do not split again unless it has failed. I do not move them to another space until I am sure the bond is strong enough, so they stay in the bonding pen for at least 2 days/nights. If you have to split them during bonding it will rarely work when you try again.
Separate at any stage if -
There is any snorting or loud teeth clacking (more aggressive form of teeth chattering), it can be moments away from a big nasty fight.
Open mouthed lunging.
Constant chasing down and biting.
Use a dustpan rather than a towel or your hand to separate them if needed.
Not working; if they have been together without fighting for an hour but...
Totally ignore each other.
Prowling up and down to prevent other pig moving freely.
Humping so much the other pig gets angry.
One pig is totally submissive but the dominant continues to reinforce with mini attacks.
Hang in there -
Humping that goes on for an hour or more.
Yawning to show teeth, not followed by too much dominance display.
Rumblestrutting and mild teeth chattering, scent marking. No chin butts.
Chin butts without other dominance displays.
Perfect partners -
On first meeting it should be interest in each other, nudging, rumblestrutting, humping. In bonding pen, lots of humping, eating and pottering about happy chatting.
Then sleeping near each other for a short nap, followed by mild humping (this is the stage many fail at and aggression builds), more eating and being quite relaxed with each other.
I have the pigs together for at least 2 nights with no problems before I let them go home together.