A car ride works by putting them both in a carrier, a small one and then going on a 20 minute car ride. Have a clean cage waiting with no stuff in it...no houses, hammocks, nothing and have it very clean with vinegar and water. Just food and water bottle and you can add a few chew toys in a few days.
Then after a week I add a house, sometimes I have to take it out because it causes fights, but eventually they get a house, shelf, maybe a hammock and some toys. The car ride supposedly works because they are so scared of the trip and just glad to be home they don't fight! I do think it works pretty well but by now I am so used to intros that I can tell if it will work or not right away. You can try a little vanilla on the noises too, and trimming the whiskers of the more dominant chin is a great help. Keep a very close eye on them for at least 2-3 days, they really can kill eachother quickly.