I'm not on my own computer now, but try this:
- Create a new stereo bus/group/send (whatever it is called in your daw) and put a stereo spectrum analyzer there (like Voxengo SPAN or something)
- Send the bass to the left channel and the guitar to the right channel
- Then see where they overlap and try to eq so that the overlap in the lowmids would be minimal
In one of my latest mix this is the final bass (unprocessed, processed):
http://www.ahjteam.com/upload/ahjteam_accell_bass.mp3
and in the beginning of the clip is one of the guitars alone:
http://www.ahjteam.com/upload/ahjteam_accell-02.mp3