I used to have a large BCI & rarely, she'd hiss when I wanted to take her out. She'd be coiled up & facing one direction...she didn't turn to try to bite me when I
reached in to stroke her coils, and after a minute or two of touching her, it was as if she'd remember that she knew me...just by my touch, and she'd quit hissing.
At that point I'd pick her up & she was always fine. (And once she was out, she seemed to enjoy it & didn't want to be put back...silly girl!) So don't stress out
over a few hisses. My BCI sounded SO fierce but she was nothing but a big cuddle-muffin.