To bond my pigs I finally had to introduce them on a "new to them" blanket, in a "new to them" room, with a lot of space, nowhere to hide, and some hay in the middle of the area. They fought until blood the first few times I tried to bond them, so I'm now quite sure that odor and space are very important, and I hadn't sufficiently prepared the space before.
They also were bonded a bit when I shampooed them both together. It was recommended, and yes, two shivering guinea pigs will huddle under a towel together. After the bath it was a few weeks before they settled down and stopped antagonizing the other.
One of the girls is obviously dominate, but the submissive sow is "happy again" after a difficult few first days. It's amazing to watch them popcorn together when I was convinced a few months ago I'd have to have separate cages!