First, thank you for your site. In the past is has helped myself and others with nice photos and how-tos for our radio issues. It is much appreciated.
When I print out 'repro' labels, I find it may be best to print on some actual vintage paper. Printing on modern, slick white paper, then trying to 'age' it with coffee, tea. or toners still might not look right.
I can find a lot of old paper, in different thickness and textures in old books. Usually toward the front or back of the book, you will find a full blank page. Already aged, different books and papers will have different colors to choose from.
Run the paper through the printer and it will amaze you
You can, for added protection, spray a flat matte finish on both sides of the paper. Then cut, glue and apply.
Using a sharp image of an old label, I might even choose to leave original stains visible. This will further add to the realistic look of a genuine label.