Bonding Methods

I have a young chin (about to turn three months) that will be finishing her quarantine next week and I hope to bond her with my much older girl (not sure exact age because she was a rescue, but my guess is about 15) who lost her cagemate recently. It's been 6 years since I've gone through a bonding process (the one and only time). I can't remember if I read the method I used on here or if I got the suggestion from the breeder I got two of my girls from, but I used a form of the side by side cage method. Set up a divider in one level of an FN with each chin on one side of it. They stayed side by side for several days and when there were no signs of aggression, I removed the divider, put an open dust bath, in they bathed and loved each other ever since. Each side of the cage just had one house double entry house, which I turned to face the divider after a day or so so they could hide out next to each other (also a suggestion from somewhere), food and water.

I still have the divider and was thinking of doing the same thing again, but have also been looking up other bonding methods. I'm just curious what others prefer and have a specific question about the car ride/smooshing method... isn't it risky if they were to start fighting in the carrier? I'm probably too cautious for that approach, but idea of that almost instant bond is appealing. Thanks for any insights!