How do you use the sequin?
Yes, you can thread 1-3 onto the hook behind a small bead and then thread wrap it tight against the bead. The bead provides support and clearance for the hook eye. More than one sequin proves extra strength as does a dab of superglue.

If you want crazy, rapala action then glue the sequins on a small pin against the pin head and then lash the pin to the hook shank so you form a lip. Tune the fly by bending the pin a bit.

A novel use is to thread them onto mono and then have it trail the fly like a parachute.