Regarding your recent Waypoints article about making your own dustless sander (see Dustless Sander, PS April 2016 online) I added a Dust Deputy (~$50 Ace Hardware) upstream of my shop vac around 3 or 4 years ago.
When applying a paste cleaner, a toothbrush is useful for buffing tight spots and working into the pores of welds; follow by buffing with a cotton cloth. A green 3M scrubby pad helps for removing more aggressive stains. Continued rusting in welded areas might indicate a developing failure, requiring replacement. Rinse thoroughly with fresh water and mild soap when done buffing.