So it does retain the finish, you just have to be careful of what I've heard called 'bloom' marks (areas where the solution dries too thickly on the surface prior to removal and causes the surface to become lighter than other parts), which is why using a mixture with less thickener makes it easier to paint evenly. Also only requires a rather thin layer per session (I cleaned it between applications).
Takes a fairly long while to clean off but detergent helps a great deal. Just use soft paper towels or cloth to avoid scratches.
Read that applying a UV-resistant, clear lacquer blocks the UV and oxygen, preventing re-yellowing but haven't tried this. Given the posts about the lifespan of the retrobrighting I'm surprised the tip hasn't shown up elsewhere that I could find though.
