I have a vastly less organised approach, but I know that I can master a lot of songs in a week if pushed.
It involves listening to the songs and bass parts until I can sing them (by which time I will generally have sussed the key, intervals etc naturally), then I pick up the bass and just literally have to play what I sing (in my head or the mrs will get stroppy ....). Only then do I get tabs/transcriptions as I have found I play better if I don’t have to rely on them.
The only annoying thing is that sometimes you listen to songs you do not particularly care for 10-15 times :), but the good thing is that you can listen during the daily commute, breaks etc. so the hours are easily put in without breaking into normal life too much.