this really can not be told on a post. i could fill up the hole form on why to do it one why and not . i could spend more time on steel and how to get it right with out filler or how to tell you how to lead it if you want. i have done it many ways and have painted boats air planes car truck cranes you name it i have painted it and have many show quality paint jobs and have used all types of paint so there are many ways to do this but i can tell you i have stuff out there that looks like the day i painted it over 15 years old so it is all in the prep .you can not get some thing flat with just a hand or a d.a it will need to be block or it will be choppy i can get things good with a d.a but it is a good d.a and this is not for the first timers