dip them in cleaning acid. You can get it at hardware store. Be careful of course.... Dip pin only in a small glass container / small glass bowl or pyrex (only about 1/8 to 1/4 depth of acid) for about 30 seconds and then neutralize in baking soda solution (water and baking soda in another glass bowl for minute or so. Wash tube with joy and water if possible. Will remove any chemicals bonded when tube was made. no need to sand and works better. Acid is cheap, couple bucks for small amount. obviously only small pin tubes - works great on NOS nine pinners.
