The ones I've done I do the floorpan first, then the door hinge pillar, then rocker. Gives you good new metal to weld to. If the cab is bolted to the frame still and you are doing one side at a time additional bracing is not really necessary, these cabs are pretty tough.
After floor pan is replaced, add the door pillar patch, tack in place and re-install door, I also like to test the rocker fit at the same time. Weld door pillar fully, either tack or sheetmetal screw rocker in place to check all gaps. Remove door, weld rocker fully.
