Just scotch tape (cellophane?), wrapped in a single, non-overlapping layer. My rifle's chambers are tight halfway along the case (not the head or the base). This method allows me to size them down just enough to chamber. They're good after that.

I could just ream out the chambers to the normalized version, but I like to leave my collection as they arrived (unless something is broken.)

I do still use Imperial sizing wax when running them up in to the die.