I just do this stuff by ear, I always have. Make a serious effort to play what you hear. The more you do it, the easier it gets. Most tabs are incorrect/incomplete.

Actually, I do have two tabs for all of these songs. Two of them, yep, they're on each side of my head, they're called ears. I find it to be a great deal easier to learn most bass lines by actually using them.

As for learning/memorizing songs, I'm not as young as I used to be so I have this little memory trick I use, whenever I want to remember something, all I really have to do is forget some other shit to make room for it ( like taking out the garbage on Thursdays, I think it's Thursdays. What was the question again?)