I am glad this case us finally solved. I barely knew of it, but after reading the thread, I became more acknowledged about it.
I was thinking as well, that if Brashers wasn't one of the two guys inside, it's plausible that they were just random "creepy weird dudes" trying to kill some time inside the shop. Additionally, they might have left the store bit before Brashers entered (Forceful enter during while the door was opened?). Also he might have even come in earlier, and hid somewhere. Like the bathroom, or sneaked into store room or something. We also know, that he did impersonate police, at least once. It would be easy for young girls first trust him enough, to allow him inside.
Also I am not 100% sure, but did they talk about one full and two partial profiles, when talking about the DNA evidence. We know one full and one partial was from virginal swap, but was there still other?
If there was, could it had been transferred possibly from Eliza? I think it was inconclusive was she sexually assaulted or not? I mean, she could have had a boyfriend, that no one knew about yet.
But yea, I think it's super likely that Brashers did commit this alone. And I think reason why Ayers might have clearly fought the hardest, could easily be, that perhaps Brashers took forceful hold of her, and by gun point, got the other girls to pushed further back on the premises. You know, like holding your arm behind your back... you girl would definitely fight back. It's even possible she managed to get loose, and that would definitely piss off the assailant. Personally, I would kick and bite, if involved in such an attack (OT: I have, thus kind of personal view.).
But was it clear that the girls were alive, when the assault took place? Even bound and gagged, they would be - in theory - able to help each other loose, while Brashers was involving himself with one girl alone. Also the timeline is short, and I would theorise, that if the girls were alive during the assault, they would try their hardest to escape. no matter how tightly bound.
OT: when I was working in restaurant business, you were most likely to open door, even after closing for delivery men, LE, Fire fighters, Ambulance staff, Repair men (if you've called them in.), Security Personnel and Postal workers delivering packages. This is why I thought about him playing a conb for the girls.... since the false sense of security.
This is just my speculations... but it could happen?