I think the best way to create a good walking bassline is to sing it first. That will give you the musical feel you want, without being constrained by any technical limitations. Then play what you sing. Knowing the theory - particularly the right notes to use to modulate between keys etc - makes it quicker and easier to play it. But whether you know the theory or not, by singing it you'll find those correct notes naturally. Well, that's my humble opinion.