I also add the mono so as not to have to fill a spool with braid yikes$$$.I usually try to put 200 yds braid over equal diameter mono so as to fill the spool.Sudsrat said:Yes!
or you can use electrical tape,sports tape etc..............
It acts as a cushion for the braided lines.So it can be wrapped tightly.
Without this cushion,the braid may have a tendency to slip on the spool.
Meaning the entire mass of braid will move around the stem of the spool.
You don't need much.