I know many breeders still recommend smooshing them together but personally I have heard bad things too (chins getting hurt or even killed). Also the idea of forcing them together with the hope of traumatizing them enough for them to bond over a shared trauma rather then try to kill each other just sounds cruel to me. That is just my personal opinion though, so I don't advise it at all, but it's up to you if you want to risk it, but make sure the vet is open for emergencies and on speed dial just in case. Maybe the breeder has some special way to do it that works without them being able to hurt each other, I do know some people swear by that method.
Unfortunately not all chins get along with all other chins, and the slower method of bringing the cages closer together over time, cage swapping, and neutral play area, etc does takes time. The whole process can take months or even years if you stick with it that long, it only tends to be a quick process with very young kits, like weanlings, or when bonding family members (but you do get the odd older chins that hit it off right away, obviously not the case here). I know some people have had luck just take a break for a few months too, just let them be in their own cages so they can see and smell each other but don't even bother trying to bond them during that time. I also know some people that have been unlucky and have chins that hate each other so much need to actually put dividers up between the cages or keep them in different rooms so they can't see each other.
How long have you had the new chin and how long have you been trying to bond them? Were they calm and ok in cages side by side before you started doing play time? You need to wait until they a both calm in cage next to each other before you put them together, otherwise they will fight. Are you giving them at least a week or so to calm down to the point that they are both ok with being side by side after each failed attempt? If you don't allow them to go back to being ok in cages side by side again before putting them back together they will just pick up where they left off. Aside from just blood drawn (which shows intent to kill), you do also have to watch for excessive chasing (more then a minute or two), excessive fur slips (more then just a little tuft), a lot of barking, and pee spraying, those are all signs playtime needs to stop and they need to calm down again before trying again. At first play time together should be very short, like 5 minutes at most, if at any point they show signs of stress or fighting they need to go back to their own cages. The behavior you are describing, attacking the bars, spraying pee, etc, are all signs they should not be allowed out of the cages together yet.
I'm not sure how you went about the introduction process so I'm not sure if that is the problem, but you can't rush the process or it will fail. Honestly at this point I would just start over back at step one. Keep them separate for 30 days just like when you first bring a new chin home, and allow both to settle back to acting normal like they were before you started trying to bond them. Once back to their old selves then you can move Scout back into the room or if already in the same room back into view of each other, cages should be as far apart as you physically can but at least a few feet apart. Then wait at least a week, or as long as it takes for them to be calm just being able to see each other. Then move them a bit closer, like 6" to a foot (depending on how far apart they are to begin with) closer together, and again wait at least a week or until they are calm. Continue to do that until the cages are side by side, but still about 4-6" apart just so they can't attack/reach each other through the bars. Once they are calm in cages side by side (ideally they should be hanging out and sleeping next to each other in their cages) then at this point you try out of cage time together in a neutral area. Again remember that to get to this point is likely going to take a couple months. If they don't calm down you may need to keep the cages farther apart so they feel comfortable.
The reason you need to start with them in different parts of the room then slowly move them closer rather then side by side right away is you don't want them to feel like their territory is being invaded, and feel the need to be on guard against the intruder. Again though, some chins are just simply not compatible no matter what you do, just like not all humans are compatible. If the personalities just don't mix it simply wont work.
