Perhaps a bit old, but still...
I like to double the basstracks and process them differently. Treating the bass as separate instruments if you will, where I have the low end, the string work and one for rounded distortion (and possibly more) I basically highpass around 40Hz most of the time, even if that's not carved in stone of course.
If necessary I then Melodyne away to get rid of any timing (and sometimes tuning) errors between kick and bass.
After this I like to compress the bass quite hard though, usually with some SSL-comp with a ratio of 10:1, with slow attack and release to really keep the wavelength firm. You could also bring out the attack with some transient modulator from, say, Sonnox or SPL.
I usually like to boost around 120 Hz if needed and maybe add some Waves maxbass for subtle bottom. Around 200 Hz I tend to find annoying frequencies where I often cut narrow. My kick normally resides around 60-80 Hz. As per Maserati's advice I also like to emphazize the importance of treble in the bass. Between 800-1200 Hz I find I could do some very slight boosting to bring out the string sound. In quite a few takes there is also some noise from the pick-ups around the baby-frequencies (3KHZ+/-) which I normally can cut away (or notch).
Distortion-wise I turn to Soundtoys Decapitator, put on the doubled track and blended to taste. Optionally using an amp-sim - often Softubes Bass Amp Room - to get it dirty.
Then automation...