Clean is a wrong term to explain this. The ribon that is coming out of the touchscreen has 4 leads. The problem of missing contac occurs between the ribon and the glass and you cannot access it.

Some people get an needle and perfurate the ribon in the 4 points that is touches the glass, in some cases the perfuration make the cupper in the ribon re-connect with the glass. It'not definive and sometimes just do not work and you have to chance the hole touchscreen.