Another DIY bloke, though before bass I played saxophone, the basics gleaned from the excellent "tune a day" book, although I did try a handful of lessons on sax I didn't really get anything from it. I also due to the above book got a very basic handle on simple treble clef tune reading.
Ironically when I got going on sax a bit I immediately started doing band stuff, and this put a kybosh on further "learning" as I simply didn't need it for the kind of playing required !
As soon as I got into playing with others I discovered bass and thought "whoah.. that's my thing" and acquired a crappy woolworths short scale bass and off I went. This was the beginning bit of the punk era so absolutely a perfect time to crack on without actually being any good, "learning on the job" shall we say !