I see that video and that’s what I did with my car:
1) Beginning with rear fenders – it’s the easiest way. I made cuts into the fender about every 2-3 inches. then hammered the pieces i cut up. After I done painted the inner lip then use special stuff to prevent rust on the places I had cut and chipped the paint off with the hammer and dremel.
2) Front fenders require more precise and accurate work. There is not really enough fender lip to cut with the dremel, so I just hammered them up and held the outside with my hand. No paint cracking and it ended up working fine.