while @Wasnex referred to his own journey (re: walking), let's not forget that his overarching point was that
it's not something that you can cram for, and then, voila: you're there.
it's a never-ending process of application (taking chances, stretching) and learning (what works, what doesn't, re: those chances you took!), back and forth, round and round, forever...
but if you can't wrap your head around the changes (e.g., standards, bop, other) then all of the great "feel and articulation" gets sucked away = fail! being able to play arpeggios is one way --- not having to play arpeggios is better! but the
changes, contextually, unlock 'the best ways'.
key concept: there are lots of "best ways!"
also, great feel (and articulation) lets your bandmates know that you can swing, but getting to the right notes at the right time lets them know that you can
play....and, maybe more importantly: who's in charge!
there is no substitute for experience = you must start getting experience! once you start = you'll never stop! and you'll know that you're making progress when you're spending less time being lost!
playing walking bass!
dive in, play with others! if you dive into the deep end with others who are more experienced: they won't let you 'drown' even if they let you take on a few gulps first (it's all experience!).
assuming you have a metronome/click (always on 2 and 4!):
a piano or keyboard + a real book = every 'safe' note for walking bass.
a piano or keyboard + a real book +
your experience and ears = all the
best notes for walking bass!
books are a good starting point as you can get 'permission' from books. but
getting some experience with others (especially more experienced players) trumps all of the books, helps you nail down the 'feel' thing, and teaches you more/better notes,
all at once!
good luck with the walking bass thing --- it's a gas!