This is really long, sorry.
Not sure of what your set up is, but it sounds like you have a fairly large area for the buns. I took a bit of an unconventional approach to bonding, one that I have not heard anyone else mention, and one that seems to be a bit of my own invention. It’s kind of a modified fast track. This may work in your situation with some modifications.
I have two boys. I originally bonded my one bun to a female, but she had trouble adapting to our household, so she ended up going back to the rescue. That bonding was a piece of cake – it took all of two hours.
The bonding with the boys was not so simple. I thought there were a lot of fights and a lot of potential for serious damage if I was not diligent about breaking up fights quickly. I expected this. These are my first two buns though, so I don’t have a lot to compare to, but I thought it was a pretty difficult bonding. There was a lot of flying fur, but no injuries to any of us.
I did a lot of research and started out with bunny dates like most people do. I was pretty determined that this was going to work one way or the other, but I was also prepared to have them live apart. I am by myself, also, so no help with the process from anyone.
I started bonding on a Sunday. Usual short dates in the bathtub went well on Sunday and Monday. Tuesday we moved to a very small expen (three panels in a triangle) and the fights began. I found the most effective thing for breaking up fights was a soda can with a couple of pennies in it. If it escalated before I could break it up, shoving the expen around and yelling HEY! in addition to the penny can usually broke them up. I broke up the fights within a few seconds if at all possible. Dates became longer, more like 45 minutes to an hour (I did not want this to go on forever, so I pushed a bit harder than maybe I should have.).
Wednesday I started with stress bonding. I used a small cat carrier on a luggage cart and pulled them around the back yard in the grass… small space, slanted surface and bumpy ride. Then we had a bonding session in a square expen, one panel per side. We moved up to 1 ½-2 hours at this point. I also introduced a litter box, but they became territorial so I took it out for a while and eventually had to add a second one. They COULD NOT eat together in there at all (but could eat together in the small carrier….hmmm).
Friday I decided to try a marathon. There was still a lot of fighting, but I could also see progress being made. One bun was giving signals of being submissive, but the other still would not trust him. My response became, if you fight, you go in the carrier for a stress bonding period. By Saturday a.m., I decided they were not ready for a marathon. Enter the unconventional part.
We continued our marathon, but in a different way. I ran errands for 3-4 hours on Saturday. They went with me in the carrier (I found there was very little fighting in the small space). I carried them around the stores or pushed them in the shopping cart doing sharp turns around corners. I picked up the carrier and put it back down for no reason other than to do it. When we got home, they sat in that carrier on top of the wash machine through three loads of laundry while I read a book. Then I started cleaning the house. Everywhere I went, even if I moved two feet away, I picked up that carrier and took it with me…all day, up and down.
That evening I had to go out for a couple of hours and did not want to undo our progress. I have a slightly larger hard sided carrier that happens to fit perfectly within their condo in such a way that neither bun could fight with the other. The door of the carrier was up against an outside wall of the condo and the air holes in the carrier are too small to get a bunny nose through. So, one bun stayed in the carrier inside the condo, and the other bun stayed in the rest of the condo…forced togetherness.
Over the next four days I rotated who stayed in the carrier and who got the condo during periods of time when I could not be home. They were forced to live with one another and get used to each other’s scents, but in a safe manner. Mind you, the condo had been my original bun’s home for several months already. I did not neutralize it in any way at any time during this process. At night, they slept together in the larger carrier on the floor next to my bed, so if a fight broke out, I could reach down and rattle them around…more forced togetherness. Pretty much, if I was at home, they were together either in a carrier being carted around the house everywhere I went, sleeping together in one at night, or having a bonding session in an expen. If I was not at home, one was in the carrier that was placed inside the shared condo, while the other one was in the rest of the condo with free access to hop on top of and around the carrier, but did not have access to the bun inside the carrier.
Therefore, pretty much from Friday night on, they lived together 24/7 one way or another. During this time, they also had extended bonding sessions of 2-3 hours each day in a fully extended expen so that they could continue working on their relationship in the larger area while also getting some time to stretch their legs. Over the course of those few days, they still fought, but the breakthrough occurred during one of the expen sessions on Sunday evening. I did not actually leave them in the condo together for the first time (with free access to each other) until Wednesday night. And I knew at that time that they were ready. The new bun just simply moved in with the old bun and the transition was seamless, although part way through the bonding process, I was thinking that the transition was going to be really challenging for them.
In 11 days I had fully bonded buns. It was a lot of hard work, but worth it. This is not an approach I would take over the course of weeks. But as an approach over the short term, it worked really well for me.
So, you might consider an enclosure within an enclosure, and forced togetherness. Perhaps a marathon stress bonding session. Think outside the box, and be determined.