For parts that I want sparkly clean, I use a sodium hydroxide oven cleaner.
I've refreshed some old heavily crusted Weber kettles using it and I'll hit my cooking grates with it once in a while to get them looking like new.
However, it is very corrosive and I wouldn't suggest using it on bare steel on a regular basis.
It's serious stuff so use gloves, don't breathe it, and keep the kids and dogs away.
A good layer of seasoning seals and protects so you don't really want to strip it off.
If the layer has become too thick, I'll scrape with a piece of wood, maybe a paint stick, or sometimes I use a ball of foil.
But I don't use water or any cleaner on the interior surfaces of my cookers except as needed to refurbish used equipment I've acquired.
