My dutch, Toot, started by fighting aggressively with Wally. She'd go up to him with the intent of biting. He would run, she would chase. I got fed up with the bonding being at a standstill this way and decided to stress bond. So I put them in the bathtub with a little water. This distracted Toot enough to leave Wally alone. I then moved them into a pen at my sister's apartment. I never separated them. I moved them over to my apartment in the kitchen (the most neutral spot I had) overnight. They didn't fight. I moved them into the living room the next day. There was a little hair pulled but no fighting, just nips and some chasing (all from Toot). I took them on a car ride and set them up at my parents' for the day. A little more hair pulling, no fighting. I took them on the car ride back home and put them in the pen in the living room (not neutral territory in the least). The nipping and rare hair pulling went on. I let them out of the pen and free range in the living room. Still nipping. The chasing had turned more into Toot would approach and Wally would run, fearing a nip. But she was no longer continuing after him. Lots of pets for both of them when they sat near each other. The nipping rapidly became less frequent and finally Toot started to groom Wally. They're still not best buds, but they are starting to like each other and I haven't seen any nipping since.
So for me the solution was an extremely extended wear them down approach. I know it wasn't the ideal bonding session, but it worked and there were no injuries. I made sure to keep two food and water dishes and two litter boxes in the pen so that neither bullied the other out of food and they had their own area to retreat to if needed. We did start off with the water bottle to squirt Toot when she nipped.. this would stop her from following through but wasn't effective long term.. she was gonna nip either way, just not if I was right there with the water bottle.
The whole process (from bath tub to grooming) took a week, but we've had Wally for 6 weeks. We did try several other methods over those 5 weeks. Switching bedding, meeting on neutral territory, meeting outside, sitting side by side petting both, ect.
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