Lots more reading today, of SWIG docs.
The main concrete thing I did was to succeed in making a SWIG .i file from scratch, and then I used it to get to where I was yesterday--getting SWIG to work (albeit with warnings). And then I managed to figure out how to make it pay attention to dependencies and inheritance. This was a little tricky for the STL, but I found how to do it (there are special .i files that ship with SWIG, that you have to include).
However, now I'm getting this pair of error for BppString.i:
BppString.i:13: Warning(402): Base class 'string' is incomplete.
/usr/share/swig1.3/typemaps/std_string.swg:17: Warning(402): Only forward declaration 'string' was found.
And there seems to be very little online with regard to this. Finally ended up shooting off a question to the SWIG mailing list, hoping one of them would have an answer.
Regardless, I think I know how to make .i files now. (Part of that is from reading through Xin's code.) And that represents actual coding (of a sort), so I feel I can actually move forward.
Pjotr also mentioned that Xin dealt with the operator warnings messages, so hopefully he's already found an answer of some kind.