i had a small 1cm dent (i mean small) in the side of the window frame in my passenger door. Just above the window line. I ended up drilling a 4mm hole in the skin of the door, then using a coat hanger which i ground the end down on, you can make a make-shift pdr screen by using that striped insulation tape along with some bluetac to put it on the window.
Simply put the striped plate on the window, so when you look at the dent you can see a reflection of the plate through the dent. The straight lines apear bent. Get the coat hanger behind the door and start pushing v gently, you can feel when its in the right spot. takes a while but when you cant see the lines being bent, its mostly out.
Be warned.... the skin of the door is v thin and easily damaged with the coat hanger, also be careful when drilling that you dont get over keen and slip through and leave a dent going outwards.
I filled this hole with a small rubber cap.
This is a technique some PDR guys use. However the nature of PDR is they avoid this where ever possible.