Well, parts made in a powder bed printer don't typically have nearly as much grain, if any. I'm a big fan of that style printer in the future, so one solution to the problem is to use those instead.
For typical FDM/FFM printers like the hobby ones you see everywhere, there are chemicals that can be used to smooth the print out.
I use my parts for robot prototypes where the function of the part is more important than cosmetics, so I don't worry about the grain. If I want a nice part though, I can use very fine layers.
that is a horrible article, considering the picture they are using is ripped off of a reprap blog on smoothing abs prints using acetone vapors. http://blog.reprap.org/2013/02/vapor-treating-abs-rp-parts.h.... (I'm actually a member of Fablocker, so I'd seen those squirrels before)
on that note though, from my experiments, acetone vapor bath does seem to strengthen abs prints some, cause it melts the surface together. Not terribly big effect, but it actually helps a lot for low infill parts and stuff.
You can give the parts a vapor bath, but you lose some of the exactness. The longer you do it the smoother the part but the more it loses it's dimensions. You are basically melting the plastic with fumes.
For typical FDM/FFM printers like the hobby ones you see everywhere, there are chemicals that can be used to smooth the print out.
I use my parts for robot prototypes where the function of the part is more important than cosmetics, so I don't worry about the grain. If I want a nice part though, I can use very fine layers.