Mig shrinkage will occur no matter how slow you go, no matter how you skip around. Those practices will HELP to curtail the issues, but will not eliminate them unless you have the welder's heat set so low that you have cold joints. Access for planishing is preferred, and also why areas such as the rocker will realize better success in replacing the entire thing. The other option is to open a hole to the back side for planishing and weld it closed afterward, where any defects are less noticeable. At this point hammering on the bead will not do much other than pounding the weld in further, requiring more filler.
