If its on your friends car, i dont see why its so hard to figure out. You dont have to tape anything off, its not going to change the way the plastic melts and forms. All you have to do is sand the edges and then heat up some metal of your choice and use it to smooth the edges to look like clear plastic and not something that was cut and sanded. A cut-off wheel, dremel, sawzall or anything of your choice to cut it doesnt really matter, your trying to over complicate something that isnt complicated. There is also a thread in dsmtooners about this as well.