I shouldn't jump in, when I can't play effectively, but when I was first trying to learn this style, I was taught to work on the thumb part first, to the exclusion of all else, until that pattern becomes automatic. Then worry about the melody lines.

Forty years later, I'm still worrying about melody lines, but, By Jingo, my thumb takes on a life of its own and does the freakin' bass lines with no help from me!!

Good luck,
Mary