I mainly use a Senior Reamer which is the second photo that Haunted posted. It works great.
Always start off with it adjusted all the way close and slowly adjust it open remove the cake a little bit at a time. Keep doing that until your cake is between the thickness of a dime and a nickle. I prefer to keep my cake around the thickness of a dime.
You do not want to remove your cake in chunks, you want to shave it off so that it is like a dust. That is why you want to go slowly and increase the diameter of the reamer by small increments. Also, you want to turn the reamer in one direction only. Don't go back and forth with it.
"When the Government Fears the People, There is Liberty;
When the People Fear the Government, There is Tyranny." - Thomas Jefferson