It's an all day process or so. Spray some ammonia on the windows and cover it with a trashbag and let it sit in the sun for a few hours. The ammonia eats the tint. After its been sitting then you use elbow grease and a scraper and scrape, scrape,and scrape. I used to live with a window tinter.
i would not ever do it myself again def. take it to the specialist who are going to put the new tint on its just a horrible experience the glue is so sticky and you have to scrape and scrape and you cant completely give up once started because you cant see out of the window to drive to the speacialist