lead foil found on high end wine bottles is the best solution.
Make the 'ribs' out of styrene and then form the lead over it. this technique works well for tank fenders with stiffening ribs pressed into them, the lead foil is formed around the original part and due to its metal properties it is easy to add realistic battle damage. Use a toothpick or something wood to form the new lead part over the form starting from the center and working outward.
The bead you pictured is sheet metal pressed in a formed steel press for added strength, these ribs or beads stiffen the sheet to save money, time, material and weight.
Some automotive modelers use this technique to make formed copies of details such as door handles for kits with them missing or poorly molded ones.
As with handling lead wash your hands after, in the state of California it is a known carcinogen.
Priming can be done with common automotive primer.
Good luck and post the WIP's! (great GB going on you may want to join in automobiles)