I didnt go by any lines,I just went for it.trying to get each side identical is kinda hard,but I have faith it will turn out ok.Dont really have a technique,used a hard rubber mallet so far,not the traditional way of doing things but I got results,As I smack it I work my way towards the center of the dent,smack at about a 45 degree angle as I go,Hopefully i will do some more this week,got all winter so I am not in a hurry.