It is good that you are switching their stuff to get them used to each other, that definitely helps. But I would recommend setting their pens up next to each other, that way they are always near each other and can get used to each other being in each other’s space more. I know that may not be ideal with the space you have (I completely understand this), but it will be worth it in the end. Try to do this in a space that Angel has explored the least.
I also had a free-roaming rabbit when we adopted our second one, so it did take her some getting used to being penned up. I would give Angel a few days to settle into this so that she doesn’t become overwhelmed with a change in her home and a new bun. Then you can start the bonding sessions.
I definitely think car rides are a great way to start off! Have a friend drive while you sit either in the back or the passenger seat with the buns. They can sit next to you in the back, or at your feet in the passenger seat. Bring an oven mitt or a small colander with a handle to break up any fights so as to avoid getting bitten your self if a fight breaks out. When you get home, either put them in the bath tub for a few minutes or on the dining table. The idea is that you do a high stress, then a low stress bonding session. This way they are all nervous from the car ride, then they come home to a neutral spot that is less stressful, forcing them to “discuss” what just happened.
Be sure to switch them daily from pen to pen to also help mingle scents and reduce territory.
While nobody wants their rabbits to fight, sometimes it happens even after all our preparations to prevent this from happening. I know it is nerve wracking to think that one may break out again, but this can be avoided by doing a few simple things: make the situation stressful enough that they are more concerned about their welfare than territory, and make it hard for them to keep a grip on each other. The car rides take care of the stress, and the tub is too slick for them to feel sure enough of their feet to really go at each other.
Good luck!