I've filled unwanted holes by pushing a round toothpick as far and as hard into the hole as possible. Then break the toothpick off and trim up outside and inside to with a hobby knife to make it smooth.
That's one way of doing it alright
Was thinking of Milliput
http://www.milliput.com/prod.htm
or
J B Weld
J-B Weld Company - J-B WELD Product Information
But i think your way is more cost effective
Would a bit of solder do i wonder?