Like if Rumlow would start stripping him but didn't bother to finish, so Bucky's t-shirt would remain pulled up on his face also restraining his arms.
Or Rumlow using a pillowcase because [your reason here] but the point is the same - with a pillowcase on his head Bucky can breath, but it's still incredibly humiliating and terrifying and he feels terrible as he is totally disoriented and in pain.

+ to Bucky also being fucked right away without being much stripped, more like half-dressed, you know, with pants lowered just enough to penetrate him and t-shirt lifted up to lay a hand on his chest etc.
++ Bucky's awkward hard-on bc sometimes it just happens during rapes irl and he can't help it