The natural state of bass neck once the strings are installed is under tension so I just usually try to keep it under tension. Most necks nowadays are pretty bomb proved.
It’s more of a thing where I don’t want to rapidly release and then re-add tension. Might be futile but I am assuming the flexing and unflexing adds more wear than keeping it under one tension.
Ha ha. I agree. I do that when I get the new instrument basses or guitars. I usually change the strings and clean and sanitize the e fingerboard before oiling it. After that they are all my gunk, which is a lot more desirable, lol.
One word of caution on fret guards though - They are usually made by punching a group out all at once on a single sheet of metal and it is a good idea when you first get them to make sure there are no burrs or sharp edges on the guards that could mark your fretboard.
For the fret wires I use a very high grit nail buffer to clean and polish the frets. Works perfectly, like a gunk eraser. StewMac even sells them but forget that, just buy them in bulk for a couple bucks. Just make sure you go high grit, a few thousand grit at minimum.
But I meant the wood. You can use fine abrasives to buff and polish unfinished/unsealed wood just fine too, so if you scuff a rosewood fretboard while polishing the frets, I have had good luck just buffing it out with the same nail buffers.
High grit nail buffers are what I am using. I have used 4/0 steel wool like @autumnsdad1990 mentioned but always felt it was still not fine enough grit wise.