And prep everything beforehand! Spray bottle to stop fights, a towel to stop fights, and a nice small area for bonding are all
This is either gonna make you think "Oh yeah, duh" or "God that woman is thick!" But cos I was taking my buns into a new and neutral area, I forgot about things like hay and water (I had toys, places for them to hide, I'd introduced them over a couple of days, all the tricky bits!!), and once they're together, if you're anything like me, you won't want to leave them for a second!!!
Also it is REALLY frightening when they fight, and your instinct is to split them straight away, but if you keep doing this it will take even longer to bond them, so leave them for as long as you can bare AS LONG AS you're sure they're not doing each other any harm.
ETA: Oooh, and also, next time I would start mine off with a small simple space, and keep them like that until I was CERTAIN they were happily bonded. I made mine a fancy NIC setup, and when they started chasing they just kept falling off shelves n stuff, I was so worried they'd hurt themselves. Even with a 4ftx5ft space it was enough room to properly throw each other around and get hurt!!