The sequence of how you walk around a car painting is really “learned”. If you understand the “why” the “how” will come to you. I started out painting lacquer completes on restorations in the late seventies. My boss preached a lot of tricks and they have provin to hold up over the years.
On a 15 coat lacquer job you definitely didn't want the dry spot in the same place with every coat, so you have to “move it around” he would say. This has always stuck in my head, move the dry spot around or "chase" it . I start at a different point every coat, so that dry spot is moved, every coat. As you enter and exit a panel, you must do this little "dance" with the dry spot.... Coaxing it along from one panel to the next.
Doing the roof first lets it stay wet while you go on. If you do the hood first and then the roof, the overspray from the roof falls on the hood and "dries" it. This is what happens with every panel, it is just on a smaller order.
As far as "carrying" the gun, this is a long learned skill. But the basis is the idea that you are a ROBOT and you are to hold the gun a certain distance from the surface of the panel. This distance MUST BE maintained. The height is the same way, as you go across the panel (commonly called "down" the panel even though you are not going "down" but across) the height MUST BE maintained. So your overlap % is maintained. These two things are what keeps each coat uniform with an equal/even about of product being applied.
So with this in mind what ever YOU do to "make" the gun do this is up to you. Some of us look like a Ballerina painting, others a mechanical robot.
All the time I spent boxing helps me a bunch. I stay on the balls of my feet with knees bent and carry the gun out in front of me. Everything that happens between the gun and the soles of my feet is a fluid motion. I watch the paint hitting the surface, and with my peripheral vision look ahead for where the gun has to go.
You need to separate the body and the gun and think about "where" the gun needs to be, your body will make it go there.
I remember watching a pinstriper (who was a childhood friends dad) stripe a very long front engine rail, he just walked backwards down the length of it with his hand flowing over the top of the rails in the same fashion I have talked about here. His Dagger brush left PERFECT stripes, it was amazing. Well holding a spray gun is no different. After a while you can walk down a 40' semni trailer and the pass you are spraying looks like that pinstripe!
Practice on a car with no paint, just move up and down (across) the panels holding the gun that perfect distance. If you waver, it isn't the end of the world, there are many factors to "makeup" for your "mistakes" but the closer you maintain the gun to perfection the better your work will be.