First, you say: "With the Sierra points they would barely adjust to just touch at the cam bottom making them impossible to adjust in spec." The rubbing block is not supposed to be in contact with the cam at the "bottom." The only measurement of significance is the point gap when the rubbing block is on the high point of the cam. (For a precision job you would like to measure the angular position of the crank when the points open, which you can do with a pointer type timing tool or by setting the flywheel on and marking the opening point on the rim.) So I suspect that you are wrongly condemning the Sierra points here. (Which is not to say they don’t have other shortcomings.

As for cleaning points: most sandpaper is made of aluminum oxide, which is an insulator, or silicon carbide, which is usually a conductor. Interesting comment about Ti02 as an insulator. A motor that’s been sitting may have a hardened oil film on the points. You can use a fine file and this is good if there is significant metal to be removed, but will not leave a very smooth surface. I usually use a strip of silicon carbide paper (the dark gray stuff, usually) doubled over to get both sides, followed by a strip of manila folder paper wet with a solvent. Best with well-used points is to take them apart and dress the surfaces on something flat like the edge of a table saw table. I like to get both points shiny-new looking and slightly convex, and aligned for contact in the middle of the pads. It takes a few minutes but they are generally as good as new. Points used to be made of platinum, or tungsten, or other expensive but durable materials. Not sure what’s used in today’s point sets.