theres many ways to do it,,,,,,,,,too many........it depends on a lot of things,,,,,angle,,,magnetic field,,,,how hot the base metal is (pre-heat) ect.....
just watch the puddle an do what ever it takes to walk it up....and once you and the whole operation becomes "one" with each other , the rest will come naturally,,,,,whatever that may be.........
This works best on 5g (bellholle) if you're pipe welding. It works great for stacking up some metal in a hurry. Watch, as it will get hot. (Start to get runny, if you're stacking a lot) I was shown (by an old timer) to hold the top part just long enough to watch the slag roll around the side of the puddle then go back and hit the sides as far back as I want to stack. I could fill out in one pass if I wanted. As far as x-ray, I don't see why it couldn't be used for x-ray. You can weld anyway you like, dance a jig even, as long as you watch your puddle, tie in your sides, stay in the puddle, and don't trap slag. You get the idea. Granted, it does leave a bit of a zigzag pattern, so I mainly use this technique for a fill pass to flush it out then put a nice nuke weave on the cap.
What are you trying to accomplish?