The special stuff is quick-setting. It also contains a cleaner primer which promotes adhesion. Regular epoxy would have the wrong thickness and be prone to thermal failure. It also takes to long to cure. You will be happier with the $3 special adhesive.
TIP: Before you clean the area, make a crayon mark on the outside of the windshield where the pad button goes. Also, be sure to remove the pad button from the mirror bracket before you start. You will need a smal screwdriver or allen wrench.
Clean the glass with a razor.
Glue just the pad on, and hang the mirror later.
Al
