My saying that the bass is a strength instrument was a quote from Billy Sheehan from way back in the day. I still believe it to be true, regardless of how many time you use the word "bunk."
And I wasn't suggesting that the OP have his fingers using dumbbells. But comparatively speaking, the effort to fret on a guitar is a fraction of the effort to fret on a bass. You just need to rest your finger on a string and it's fretted. It does require more effort for bass. Again, it doesn't take an enormous amount, but for someone coming from 20 years of guitar, he's almost pre-programmed for a lighter touch.
As far as those "silly" spring-loaded "bunk", they aren't for strengthening as much as increasing finger dexterity/speed. I have one. Had it since it first hit the market at the end of the 80's. Very helpful with increasing my dexterity. I haven't used it in 20 years, but it was helpful when I first started out.
Hey, sorry for the 'bunk' loaded response.
I do know that those spring things are gimmicks and do not do one bit of good for people trying to develop good bass or guitar technique. Finger strength is a byproduct of playing bass. But concluding that you need extraordinary strength to play bass is backwards. You get stronger fingers from playing bass, but you don't build strong fingers so you can play bass and focusing on 'strength training' is misguided when it's not strongly offset by solid technique.
I also know that the bass guitar (not upright) is not a "strength" instrument in spite of what Billy Sheehan might say. He's a monster player - and playing bass like he does may include an elevated strength quotient - but it's not a requirement - and there are players who play on par with Billy who do it without exerting extraordinary amounts of strength. Doing crazy, high-speed hammer-ons while bending strings across the entire width of the fingerboard does indeed require strength - but I'd offer that that is not the way MOST bass players play nor is it what MOST bass parts demand from a bass player.
Upright clearly requires more finger strength than almost any other instrument - but upright is a very different beast than almost every other instrument - obviously. Bass guitar, fretless bass, electric/acoustic guitar - all require a moderate amount of pressure to make notes. None of these instruments require extraordinary strength and saying they do sends people down paths that really don't do anything more than keep spring-loaded finger strengtheners in business.
As a matter of fact, one of the most beneficial exercises you can do as a bass player is to focus on the opposite of "strength" - how to play with as little pressure as you can.
To the OP - basses can be noisy. Round-wound strings make noise when you slide over them. If your neck's relief isn't set right you can get buzzing and clacky-sounding fret noise. Poor fretting/fingering technique and poor plucking/picking technique can also add unwanted noise to your playing.
You need to start with an instrument that is not working against you. That means getting it set up properly. It is something you can do yourself, but if you are not comfortable with that you can have it done for you - and it's worth it. IF it is your setup that's the problem, fixing it will be like getting a new set of hands - you will be amazed.
IF the setup is not the issue - then you need to look at your technique - ideally with a bass teacher - not a guitar turned bass teacher (or if at least a guitar turned bass teacher who is not just trying to apply guitar technique to bass playing) - who will show you how to almost effortlessly play your instrument, quietly, forcefully, aggressively, delicately and prove that strength is about 20th on the list of things you should focus on - if at all - and that it's actually something you can pretty much ignore - because if you are practicing good technique, your hands will develop the exact amount of 'strength' they need, no springs attached.
