It occurs to me to wonder if that Gunze Sangyo Mr. Surfacer mentioned in another thread, applied over a (shapeways?) 3D printed surface might be just the ticket to smoothing things out without destroying items like rivets.

(I have heard of Mr. Surfacer elsewhere, and a can of it sits on my shelf waiting for it's chance)

But certainly all of these items I have ever seen have not been anywhere close to smooth enough for final use as a round or curved item. And as an engineer I have seen a bunch. (Though as Dennis commented - orientation is key. Print your cylindrical tank vertically, then the layers should be less noticeable.)

Now, when one can simulate wood grain in 1/87th...

That said, I intend to make some bits via Shapeways in the next little while...test drive it.

Just thinking out loud...Have Fun
Steve Wintner