Due to my career as a full-time educator of both youth and adults spanning 2.5 decades, as well as the need to get formal education in a lot of different disciplines I tend to learn a lot on my own now -- and sometimes with a private teacher if I can't figure it out myself at first.
I started with a teacher on piano for eight years, and took 8 of 10 exams at a conservatory in Canada. While not bass education, it is where i learned to read bass clef and chords.
I joined our high school stage band, and had a very encouraging high school music teacher. I formed a weird quintet (bass, drums, trombone, trumpet and sax) formed. After he heard us playing "Some Skunk Funk" (a bunch of 15 and 16 year olds), he invested in us, and we played all over town and won a stage band festival he flew us out to. This guy improved my playing by critiquing my playing from a band perspective.
I left the instrument for about 6 years, and then started learning from a book. Since we can't name names, I won't say the book name, but the guy is a well-known writer and former professor at Berkley, I believe. He is probably my favorite jazz educator on the planet He epitomizes what 25 years of full time teaching in other disciplines has taught me. As Einstein said "True genius is found in taking the complex, and making it simple". This teacher did that. He eased me into improvisation with this book, even though it was only quarter note improvisation. I had tried learning out of other books on walking , but it never stuck. But this particular book was genius in its simplicity, ending with my learning 10 standards I could play fluidly on the fly.
I then took lessons at an online school from a well-known fusion player. This really helped me understand improvisation better.
Then I started forming groups, and my education accelerated. I learned more jazz-oriented theory from these jazz guys who were actually quite knowledgeable. We started attracting (and hiring!) the prominent, local jazz musicians and I learned more and more from them. I'd ask as many questions as I thought they would tolerate, and learned much. One guy used to play with Tommy Dorsey orchestra and gave me an old school perspective. While not formal teachers, they give you feedback pretty quick when you don't play well.
Then I picked up the upright bass, and took a few lessons with a very encouraging private teacher. I had made the decision to go with a smaller instrument, and he accepted me and encouraged me. He gave me enough that I was able to convert my electric bass jazz repertoire to upright and gig regularly. I found that much of what he taught me was available on Youtube, but it was his encouragement that I think made a big difference. He helped me progress rapidly.
I find I spend my time learning new tunes for performing. Performing is what drives, and motivates my learning. And of course, being the business motor of several different groups, as well as my non-profit work makes practice time precious -- and efficient.