I learned playing guitar at first, but nowadays I play guitar mostly for recording and bass as my maininstrument.
I am a way better bass player than a guitar player, I even can't sweep on a guitar, but I can sweep on a bass...
Had a few lessons from my uncle (started playing upright bass with 15, played 10 years in an orchestra and in many different jazz bands, e-bass, too) that helped me alot.
Especially the right hand techniques, left hand is not a real difference to guitar playing (talking about e-bass, not upright).
The most good guitar players I know are acceptable bass players, but only a few of them play bass and not just a "4 stringed, downtuned guitar".
In my opinion it really helps to play groovy stuff at the beginning before trying to copy ultra technical guitar riffs.
This will let you think more "bassplayerish".
Just my 2 cents, and I don't want to sound selfish, there are way better bassplayers than me everywhere but the bass is the only instrument I am able to play that even guys that play it thereself think that I am acceptable and not just total noobs