Just intro them in the same cage. If they even out quickly, leave them in it. Don't remove/reintroduce as they'll start their scent marking and rumble-strut routine all over again, every time.
Get several small boxes, and cut 4 doors into each (so a door flap or arch opening) and place each at different points in the cage (they might move them, flip them, etc., just put back) with the box top on the bedding. Get 2 water bottles, opposite ends of the cage, nearest each box. Two food bowls. If they start tipping the food bowls constantly (an irritating habit once they learn it), consider switching to a large Frisbee flipped over like a plate. I use them now in several cages after too many figured out how to flip the smaller pet bowls, and they'll all line up, evenly spaced from each other i.e. North/East/South/West or in a star formation, or directly across from each other, etc.. Depends how many are eating at the same time. They're big enough to accommodate numerous eaters w/o whining/fussing.
Being "mean" is subjective. They are establishing hierarchy. One is top-dog, other isn't. Numerous boxes with plenty of openings, the dominant one might chase the lesser one out, but that's the idea. Need a big cage. As long as they aren't getting in circle fights with blood drawn, let them work it out.
for two boars you want about 160cm in length by about 60cm width. Have a look at c and c cages. This could sort the issue between them. Its a well known issue that small cages cause boars to fight.
