Interesting, but these models are resin castings of 3D printed originals (I think). So would the acetone trick work here, I think not?
Anyways, thanks for the ideas. I will certainly by so LGS from my, er... LGS to try out. And I can get Mr. Surfacer when I order some other modelling stuff from a certain webshop.
I examined the models more closely, I have three different ones. And they don't all show the lines so badly, and it looks like on one of them the manufacturer had done some cleaning up too. The two others are pretty bad, in that they look like they require a lot of elbow grease to get every line out by scraping and sanding. So certainly some kind of leveling agent would make things easier.