"It isn't a reflection on Indonesia or China or wherever." Hear hear to this. You can get both ends of the quality spectrum from these locations. It's the companies that cut the financial corners.
GHS pressurewounds v Rotosound 55 solobass pressurewounds:
Rotosounds are brighter, grippier, and have a lesser degree of pressurewound-ness resulting in more string noise like rounds. And maybe under a bit more tension.
Practice separately. I find initially humming along to melody helps, in transition. I play a bit of harmonica, same thing although I thought it'd be easier. Nope. I find both for singing and harmonica, strumming along with guitar helps.
I echo much of the rest of the comments. The bassline has to automatic. My penultimate step is humming along with the bassline and, keep the metronome on. I usually end up practicing the song too fast. Working on Eight Days a Week now.
Saw a Beatles tribute band once and the "Paul" played the viola bass left handed. Didn't look quite natural but it was very effective. He then played, Yesterday, solo and switched to his natural, I think, RH playing. I was impressed.