I've used just about every brand of pin stiping tape you can get. The only thing I've ever had good luck with is auto pin striping tape by 3M. I buy it from an auto paint store, not the "Autozone's" on every corner. I've never had any luck with the modeling tapes. Using auto tape, I never have to seal it, but you should set it in the sun for a while to let it cure. As far as decals, I seldom clear coat them, but if you do, be sure to "scuff" them with a Scotch Brite pad or the clear will not stick. Good luck.

pmw