Well, this is a great topic because the power of dynamics is underestimated most of the time but is what make the bassist Tone.
That's because it's the fundament of the bass playing no matter what.
A good starting point for each bass player should be a bass line almost even, dynamically talking (both groove and solo).
It's disappointing when you watch some live performances and you hear a bass player playing some steady rock groove and sometimes you hear the notes, sometimes not, or a funk fingerstyle player missing some sixteenth notes or a bassist playing some active slap groove/solo and be able only to listen the plucks, it never happened to you?
I always suggest to my students wishing to improve their dynamics, to record themselves; a good test is a medium rock eight line or a slap groove and then check the dynamics and timing.
Coming back to your questions, as I read on a previous post, you should be already at a good point.
A good way to start emphasizes your dynamics is playing scales and arpeggios singing the notes (hear training concepts).
Play and sing first equally each note then play the scale with a soft/medium dynamics and strongly the arpeggio note.
This would be a good exercise to begin, especially if you apply it to your all harmony knowledge and over the whole fingerboard.
Then you could go ahead making your personal combination, let always your hear and feel be the judge.
After that, there is another couple of matter very important about dynamics.
First, your band fellas. A lot of times even if you are great with dynamics, the band members are not, you can play all the dynamics you want but if the drummer or the guitarist doesn't listen to you, or each other, or don't give to the tune a dynamic form, your playing will be affected, no matter what.
Second, strings and action. In my opinion, the strings type (flatwound, roundwound etc) are not influent on dynamics, new or older strings definitely have a part on it.
The same thing for the bass action, if you learn how to handle your strength with a medium/low action you will definitely reach an improvement in dynamics. Of course, you can do the same with high action, but probably the instruments will less response to your touch.
I hope that helps and if you need more help feel free to contact me.
Ciao. Enrico