One of the next steps in my Mauser rebuild is Bluing. I have decided I would like to try my hand at doing myself and am gathering information at the moment. My options given my budget are Herters Belgian, Mark Lee Express or traditional slow bluing. I am steering away from Belgian due to the Mercury content the express however seems like a reasonable option. Is there a big difference in durability between a slow blue and express? Any other pros and cons? Any other products I should be looking at?