I have never had a problem with the V2 staining any of my wash media.
The only problem I have ever had was I left a uber sponge in a bucket submerged and it turned it blue.
My media comes clean everytime.
I wash both of my cars every weekend with ONR.
Yeah. I did both my mini coopers.
Check out the forums over at tintdude.
Invest in a good roll of tint that will last.
Just like detailing you can learn to do it well it's going to take practice.
Having the right tools makes it easier.