I had good experience using ocaml-ctypes and I would definitively use it if I had to deliver a large binding under time pressure. But on the other hand I adds a non-trivial layer that you could end up having to understand (there’s a paper about it here).
So personally I still often write my bindings with the bare OCaml FFI. Because I have a reasonable understanding of it and less dependencies means less bitrot in my projects. While it is certainly more error prone, it’s not so hard to use if you follow the rules and don’t try to be smart.