Motorola VT-71 restoration advice needed

[Mars777]

Hi all:

I am in the process of chassis cleaning of the copper coating. I never cleaned a copper coated chassis before. Though I am having success in using Brasso.
There are 2 concerns that I have before I go any further:
1) How thin is the coating on the TS-4J chassis and is there any danger of it being rubbed off?
2) I haven't cleaned any area as of yet that has printing. Will Brasso take off the printing? Please look at the picture to see what I mean.

TIA!
Tom