Your gun is worn because it's used - that's ok.
Painting a gun is never a good idea.
While I wholeheartedly agree with your first point, I’d disagree with you second.
If someone wants to paint their gun and they’re happy with it, it’s a good idea. If not, it’s just spray paint and can be removed (doing so might not be much fun though).
I gave the rattle can treatment to a 10/22 because my son thought it would look cool (he was 9). It’s worn off here and there, sure, but it’s not some heirloom piece that can’t be replaced. And when it wears, I can always hit it with another blast of paint.
Blast away with the krylon if you want, just realize it won’t be durable, there are better options for not a ton of money more, and you’ll likely have a harder time selling the gun should you ever decide you want to.