Howdy Stevesleather
'wetting' your leather is a practice thing. Don't over wet it or will get spongy and the tools won't make a good impression. I found that I dampen my leather and try to keep it covered to prevent drying out as much as possible. When I was getting started, I over wetted the piece and it always looked 'crappy'. When the water content is 'just right', when you strike your tool, it will burnish [a dark brown] as you go.
Again, it's a practice thing.
Hope this helps
Happy tooling
Tim