Next go to 320-grit sandpaper. If you didn’t have deep scratches or dents to start with, you could have started with the 320, rather than the 240. If you can start with a higher grit, that’s best, it just depends on how many scratches you have. Like the 240, primarily sand out the area that was repaired and feather it out a bit. The paper clogs up quickly, so you have to keep moving your sandpaper around so that fresh sandpaper hits the surface.
Sand in the same direction without cross sanding, which will help overall when the light refracts. After 320 go to 400-grit. You could go to 600-grit at this point, but Cody finds that using 400 helps make the jump to 600 a little easier. Again sand in one direction. The more time you spend on a piece, the nicer the end product will be. At this point, you will see the metal starting to smooth out and look like a satin finish.
Next go to 600-grit. Use a water squirt bottle to wet your sandpaper. This helps the stainless not to clog the paper as much. The shavings are carried away a little easier, so the 600 lasts a little longer. Wipe and check to see if there are any scratches remaining. If so, you can back up and repeat earlier steps as needed.
800-grit is the next and last hand step. Squirt the 800 with water. Now we are just trying to take out the 600 scratches.
Note: if you have a piece of metal without a lot of damage, start with an 800 or even 1000-grit sandpaper. It will save you time and money.
For the next step don additional protective clothing: heavy jacket, gloves.
Take a Dual Action (DA) sander, and while controlling the speed, slowly sand back and forth while making sure the blade is always moving toward the edge of the material.
Repeat the last process with 1200 and 1500-grit sandpapers. End of Part 2. See Part 3
Video and information courtesy of Automotive Restoration Club