Apparently a well tied, clean figure 8 will not need a backup knot...just a nice little tail.
For me, I like a half fisherman's knot in the tail for psychological reasons.
I am sure you will get a myriad of opinions on the merits of a variety of backups...rewoven, glued, tied and stapled.
Bottom line is if it makes you feel better and push harder...do what works for you.