I will warn against using sand paper. These abrasives always sacrifice some of their grit which embeds into the metal. This grit is not conductive to electrical current and doesn’t melt away. At best it reduces metal contact area which increases heating of the remaining contact surface. At worst, the grit stands proud blocking full closure and further reducing contact area in large places.
In short, embedded grit really decreases point life. If you must sand, be aware you’ll need to replace the points soon or that you will be disappointed in point life expectancy and the need to keep dressing the point contacts frequently.
Point files, being being metal, are conductive, leaving any bits of itself in the contact surface to no electrical detriment.
