Smoothing Body Seams

I would like to shave or smooth out the seams between all the exterior side body panels... what's the way to do it?

I have noticed the panel flanges in the walls have rust (like a lot of the van!), but I assume they provide rigidity for the panels... prevent them from flopping around under turbulence. But back to the topic, is this a bondo job, or do I get to run tack welds to fill the seams?

Thanx

Or is it an illusion that the seams are filled, because of the paint job quality? For example (Mike), I thought Vanishing Breed had invisible seams...