Wow I am glad I pulled up this thread again. I have joined a band where a 5 is almost mandatory. I have had a beautiful Stingray 5 for a few years that I have never really spent the time to get used to it as I feel more natural on a 4. I see I just need to spend more time on it. Tonight is the only second night I have played it in a couple of years and I was ready to throw it in the trash. I have a hard time keeping strings quiet and finding notes that I can't see. I get lost in the lower strings somehow. More will be revealed I hope.............it will be really useful for a band of modern rock covers.
When I got my first 5 string bass.
I was excited to have the new bass and it to a practice and it was a disaster. At the time, I didn't have the fretboard knowledge that I have now. I had "Panic Position" and "Panic Notes", when I would get lost, my Panic position was middle finger on the G and then I knew where I was. As you can imagine, that panic position didn't work well on the 5 because I was now on D.
Until I could acquire a much better fretboard knowledge, I put the 4 in the closet and forced myself to only play the 5 for a solid month. I also worked on changing my "Panic Position" to the "E" on the "A" string which ends up almost center of fretboard both vertically and horizontally.
I worked on fretboard knowledge from there outward until I had a very good fretboard knowledge and no longer have or needed a "Panic Position".
When you first switch, you will have to get your brain used to that closest string not being an "E". That might take a couple weeks. Put your 4 in the closet and only practice with the 5 for a while. Try to learn where the notes you already play are located on the low "B" string. Try refingering familiar songs E at the 5th fret, play the G at the 8th fret... etc... That will help acquaint your brain and fingers with the new string.
At first just play the stuff you already play and don't make any special attempt to "Play those low notes". When I first got a 5, I way overused those low notes.
Try fingering the songs that don't need the low notes further up the neck so you are using the B string in the same register, but farther up and on a lower string. You will automatically start using those lower notes where they fit best. You will find that using the E, G, etc... on the B string will give you a fatter rounder sound that the E string, which will give you different tonal options.
Of course there are times where you just know that hammering that low "B" really fits the song. Use it, don't be afraid of it.
As far as keeping strings quiet, as you get more strings, that becomes more of an issue. I play 99% finger style and used to plant my thumb on the top of the pickup. I saw a video on Youtube about a "Floating Thumb" technique. You use your fretting hand to mute the strings that are higher than where you are playing and use your thumb of your plucking hand to mute the notes lower. I typically rest the tip of my thumb on the B string when I am playing on the E string and if I am playing on the A string, rest the thumb on the E with the side touching the B. The floating thumb technique really helps with extra strings ringing. If you play pick style... I have no good advice there because I suck at that. Palm muting is what works there... I guess.