SpudFiles

Do slide valves need maintenance? I feel like mine isn't as smooth to pull as it was the day I got it. I feel a tiny bit of friction, is this normal? Can I put any type of lubricant on it to make it smooth again?

They don't necessarily need maintenance, but they can benefit from it.

I personally use silicone grease for these things, but you can probably get away with something petroleum based. While petroleum products do damage natural rubbers, it's exceptionally unlikely that any seals in a slide valve are natural rubber.