You can use Acetone to smooth the model, but this often smoothes out the details as well.

I prefer sanding. Or printing fine enough, but that's not easy. 

The model I posted above wasn't cleaned up because I'm trying to find the right parameters for printing that fine, and it's easier to see if it improved if the comparison model isn's cleaned up. At the moment I either get fine threads or the swords break while printing. Well, you live to learn, right?

That being said, 3d printing is something which needs to be learned. The slicer software which computes the tool path has enough parameters to play with, different kinds of plastic need different parameters. It took me about a year to get good prints out of my machine, reliable and not just lucky prints. You can probably shorten that time if you buy a preassembled printer like the Ultimaker or the Makerbot - but then, you cannot improve your machine and you pay much more money. There are very good kits for about 800 Euros out there, which are much better than what I started with.

A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
-"Amazing Grace" Hopper

Avatar image of me done by Chidori.