Yeah, I don't agree with the no valve rotation thing. I bought a '47 Conn New York Symphony that had angry slow valves.
I used some low viscosity toothpaste and a ton of old valve oil to lap the valves. I went straight up and down using the guides and then spun them all around in a lapping frenzy.
It did correct my sluggish vlave issues and as far as I can tell there has been no damage to the valves. I use Hetmans synthetic (classic), the valves are very smooth now.
I have used a lot of smilies in this post but don't know how I feel about them.
