The guy who taught me stock work emphasized to always use a backer of some kind when sanding which applies to both wood and metal. His suggestion for curves was a selection of tubing from the auto parts store. The smallest vacuum line is about 1/4” OD, the larger heater hoses are about an inch, with many choices in between. He was correct, and it works.
Edit- the blocky style of pencil erasers, IE the sharp corner rectangular gum and slash cut pink and white also make excellent backers.

Dave,

Great work, and a great post!  I seem to recall reading somewhere that small pits can be filled with solder for parts that are to be plated, but I can claim no first hand knowledge as to whether it would actually work.

If you use the newer soft solder that is (Usually) 95% tin/ 5% silver to fill in voids, etc. that will take plating nicely.

A soft solder with Lead/Tin can sometimes work if the Tin content is high.

The factorys sometimes filled small irregularitys with Brass/Brazing. That of course plates as well.

Even Hard Solder will work well. You don't need quite as much heat to use it, but still in the 1100/1300F melt/flow range.

When polishing out the above repairs, always use  hard backed polishing techniques. If not used, the softer solder or Braze repairs will end up with cupped out surfaces when polishing with the surrounding steel.

If you are finished polishing and before you apply the final finish no matter what it is,,run the part lightly over a wire wheel with the surface of the part smeared with a thin coat of oil.
Any oil will do,,WD40, 3-1, motor oil, 'gun' oil...
A 'fine' wire wheel as is usually sold in most hardware and Box Stores works well.
An old carding wheel also works. Don't use the good one you use for Rust Blue carding!

Light pressure and non-directional working the surface will softly blend all the polishing grit marks.
It will leave you with what was called a burnished polish. 
You can brighten it up even more afterwards with a simple rub down with simichrome on a 0000 steel wool pad.

One thing the oil/wirewheel technique will do as well is to relveal any grit marks /scars/file marks you may have missed on your march thru the grit sizes.
Any problem will show up as a dark mark and can be then resolved with further hand polishing back thru the grit sizes.

Using the wirewheel/oil technique will not round edges nor dish out holes if you apply with light pressure. It won't harm lettering ,

The oil/wire wheel technique was one used by many of the old rifle builders. They often left the metal as is after that procedure and Rust Blued with that as a final metal finish.

Are those pennies I see? Well you have taught me something else...



JMH