I have done a good bit on DXF importing in to Cinema and I have to say it is usually difficult. Sorry. I love C4D, but this is not a strong point.
What kind of luck have you had so far? I say this because my experience has been that getting a file in to C4D has everything to do with what is in the file, line types, DB calls, even the DXF version. I have had the same drawing open when saved in version 2000, but not 14. It should be the other way around?!?
My best luck has been to manipulate the drawings in AutoCad, or LT, or even Sketch in to logical items. Your AutoCad drawing may be for the cubicle, desk, filing cabinet, etc. Break them down in to new/different files with nothing in them but the splines your need. Then put the objects back together in C4D. I haven’t had any trouble with flipped faces, you may need to ‘Align Normals’. I think you have to do this before you ‘connect’ the splines. I do run into occasional scale differences though.
Good luck. I would love to hear how it works out for you.