Its not that big of a deal . Unless your literally removing material, it will be fine . It will help make it smoother but its not going to help shorten the pull length or change the pull weight . The area that needs polished is the very front face of the trigger . Not the top ,nothing contacts that area. Then on the hammer where the trigger contacts it , this is a very small area and you do not want to remove any metal in this area .
When you pull the trigger / hammer assembly out you will see where the 2 parts contact each other ,those are what needs cleaned up and polished . Dont expect it to turn it into a 3#, $250 trigger its not going to happen . If thats what you truly want you will need to buy a quality trigger assembly .
Criminals Prefer Unarmerd Victims....
And Dictators Prefer Unarmed Citizens