Information that I thought someone might find useful. If your Bathroom or Kitchen sink shows tons of scratches and/or no longer shines ~ here is the system to restore it to the "like new" look.
Note: This process will actually take only about 1/2 hour... 1 hour for a double kitchen sink.
No need to add excess pressure to the buffer when using... let the sandpaper and polishes do the work.
Step one: use 600 grit wet/dry sandpaper and a 6-7" buffer/polisher to take down the surface to just below the scratches. Use it WET in all the Steps.(Sandpaper is available in your local auto parts store)
I cut an 8 1/2 x 11 sheet into 4 pieces (8 1/2" x 2 3/4") and fold the strip into thirds... then simply lay on the surface, set the buffer on it hit start. It will slip out a few times but just reposition and continue.
Step two: At the point you feel all of the scratches have been removed... change to 1500 grit wet/dry sandpaper and go over the surface again. This will take off 95% of the roughness left by the 600 grit.
Step three: Now switch to 2000 grit wet/dry sandpaper and go over the surface again.
Step four: Add a buffing pad and go over the surface with a "Medium Cut" rubbing compound. The one I use is made by 3M and available at my local auto parts store. Note: Using a Heavy duty rubbing compound will only dull the surface and using a Polishing compound will do nothing. You must use a "Medium Cut" compound. This will bring out 90% of the final shine.
Step five: Now - using the same pad - go over the surface with a fine-cut cleaner. I use Mequiar's Mirror Glaze Fine-Cut Cleaner. This step brings out the actual final shine again.
Step six: Coat your finished and shiny sink with Gel-Gloss - Fiberglass, Marble & Acrylic one-step cleaner & polish. This should be available at your local hardware store.
Done ~ If you still have very noticeable scratches, you will need to repeat the entire process again...although this is a multi-step process... your actual time will only be about 1/2 hour.

This same process will work for bringing back the shine to a Stainless Steel Kitchen sink... but omit the last step of adding Gel-Gloss.