Prep for touch up paint

[nookandcrannycar]

Ugh. After recently dodging a bullet, so to speak, re getting scratches from vandalism buffed out for free....I now have a side ding (happened in a different city) that 'chipped down to the metal'. My '14 Yaris (already added by the distributor for FL, IIRC) has that 'clear bra film' over the front bumper, both doors, and much of the rear bumper. I imagine a preoccupied kid was in the rear passenger seat of a 4 door and carelessly opened the door into the side (to the rear of the door) of my '14. My sales rep in Florida showed me how to best apply the touch up paint, but I don't remember anything re prepping for that. Should I get the car washed beforehand? Should I just put water on a cloth and wipe it? If so, what type odf cloth would be best. I might be over thinking this ?