My first fuselage was 4130 and gas welded. I am starting a new project and decided this time to do it with TIG. Basically, I am relearning to weld so I haven't really started yet. My question is this; with gas the mill scale wasn't a problem and just burned off during welding. Now with TIG everyone says to clean the tubing of mill scale. Now maybe I am mistaking the grey coating the tube has with mill scale OR I am to make the tube bright and shiny? Just what do I use to clean the tube? How clean should I get it? I assume a pneumatic grinder with a steel brush on it would damage the tube. What is best practice? What is clean for 4130?

Thanks!