How does Ford overcome the issues with their pickups?
Disclaimer, I have not been involved directly with the Ford aluminum body-in-white program. But ...
The Ford trucks are aluminum body over steel frame. There are other vehicles with aluminum unibodies, but it doesn't really change anything.
There's the part of a body-in-white that you see, and there's the structural part underneath that you don't see. The bit that you see, needs what the auto industry calls a "class A" finish. What's underneath, doesn't matter so much because it's hidden. Most unibodies are pretty ugly when you take the outer skin off ...
The structural part that you don't see, with a steel structure, is usually spot-welded together, although sometimes they're laser-welded. Adhesives are pretty common, too. Seals the spot-weld from corrosion, fills the gap, tends to cut down on noise transmission.
With an aluminum bodyshell, the structural bits underneath can be attached to each other by various combinations of structural adhesives, riveting, hemming (folding the edge of one panel over the edge of another), bolting, etc. It can be ugly, as long as it's dimensionally accurate. Once the ugly structural bit underneath is ready, then you attach the "class A" skin on top of it. Front fenders are almost always just bolted on ... that's easy. Door panels, hood panels, and the like usually have a stripe of adhesive applied around the edges and then hemmed (edge folded) over the structural piece underneath - and that's the same whether it's steel or aluminum. On most cars, if you open one of the doors and look carefully at the inside of the outer edge of the door, you can see where the outer panel has been folded over the structural inner, with adhesive filling it up. Same whether it's steel or aluminum.
Know how most cars have a trim piece for the full length along each side of the roof just inboard of the top of the doors, all the way from the top of the windshield to the top of the tailgate or rear glass? That's there to cover up an ugly joint where the outer roof panel and the outer side panel are both joined to the inner structure underneath ... It's easier to leave it ugly and put that trim piece over it, than it is to make it pretty.
Aluminum needs a different primer coat to get the paint to stick. Once it's past primer, painting is the same as for any other vehicle.
