It is not necessary to seal your finished pieces. However, you are able to protect pieces that will be handled frequently with a polyurethane sealer. See attached all about sealants. Shrink Movie Sealer FAQ
What type of markers/media work best on Shrink Film?
Permanent markers/pens work top on non-Inkjet styles of Shrink movie.
My Shrink Film curled up, what do i actually do?
Shrink movie will flake out, after that flatten back away, this is merely area of the shrinking process. Show patience while shrinking and watch for it to flatten out. If the film curls and sticks to it self, simply eliminate through the oven and using toothpicks or tweezers un-stick and send it back on oven. Placing huge body weight vellum or piece of parchment paper along with work while shrinking will minimize curling and sticking. Keep a spatula helpful whenever shrinking to be able to utilize it to flatten tasks since they are taken out of the oven but still hot.