Bubble free muster? See my Rezi

Clean cell phone so that you can see no more dust. Then stick the foil and using a credit card (best wrapped with Zewa) smooth. Apart still got somewhere speck of dust under the film then simply peel it off again at the appropriate point. Then simply dab said point with the back of a piece of adhesive and stick back, so you get guarantee a perfect result.

Did the film testweise withdrawn several times and re-glued, it adheres again like the first time.