Microstation doesn't really have a "lofting" command, but your suggestion about sections is good, and is often the strategy I've used. There's no magic pill - it takes a lot of work:

DELETED TO REDUCE CONFUSION *

All of this can get very complicated by the fact that MicroStation will often not recognize an extruded surface - only the plane geometry used to generate the extrusion.

DELETED TO REDUCE CONFUSION *

Like I said, I stay away from the b-splines unless there's no other way it can be done.



* I had a very long description that was not much help after thinking about it. Please look at the method below, instead. It is quite possible in MiscroStation SE, and perhaps earlier versions. You should have no problem with Mstn/J.