For hardware, I just use a soft dry cloth. If it needs more cleaning, an old tooth brush (clean all tooth paste off first) with a bit of rubbing alcohol normally does a good job. I think the wise approach is to go from least aggressive methods to more aggressive. I've replaced hardware on two basses just because they got so nasty and worn out that there was no hope for them otherwise.
But the bass I've had longest and played most (see picture) still has all original hardware on it. I only use a little lemon oil or tung oil on the fretboard. The rest just gets a little cleaning with dry microfiber or a bit of warm water applied to a clean soft cloth.
The electronics went out some years ago and I could not get replacement TUNE parts, so I had a local luthier install Epic Custom pickups and a new passive system. It sounds different from when it was active, but I think it sounds very good.
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