Filling cut-out cover pits with solder

[Colonel Biggs]

I have an original cut-out cover that is perfect, except for a few small pits in places. I used some plumbing solder that I had available, flux, and a butane torch (heating from inside the cover) to melt some solder into place. This worked until I went to sand it smooth after cooling. The solder would tear away in pieces. Is this a function of the type of solder, or am I missing something else? This would seem to be a no-brainer (it says here).

I also want to fill some pits in an instrument panel that I plan to plate. I'm not sure that the copper plating stage of the process will be sufficient to hide the pits though.

Gordon