Well, he'll flail around a bit, but all they have to do is conk him on the head before he can really manifest the Oricalchos. Surprise him on his bike/on the street and he won't have time to freak out enough to manifest it. After that it's just a matter of keeping him either too dazed to focus or not scared/pissed enough.

I'm tempted to say he has his deck on him...I guess that could go two ways. Buffyverse vamps don't have souls, right? So even if he had it, he couldn't take his captors' souls ahahahaha nanner. But if he has it, it puts the Major at risk if he wanders by in person because holy crap his face will totally trigger the Oricalchos.