Doswonk,
I use a multitude of different things to clean mold lines - just depends on where they are - scraping carefully with a no.11 blade, sandpaper of differing grits, sanding sticks and files are what I use.
Often a very light brush with liquid cement over the area of the part that's been "cleaned" will bring back a shiny surface that matches the un-sanded area, making the final painting easier and tidier.
I get my sandpaper from the auto parts store - they have some really seriously fine paper - up to 2000 grit wet or dry - and it's cheaper than the Tamiya or Testors hobby sandpaper
Cheers, Lee Tree