Stratasys offer a smoothing station for around $40,000 but I wanted something a little cheaper....
There are a few others on the net getting very good results with putting models in a cheap deep fryer or cooker and heating a small amount of acetone for a short period to vaporise the acetone and smooth the model.
Another option is to place the model in a sealed container with some acetone, and leave for a few hours. This method is the cheapest, but also the slowest.
A few things about acetone vapour. Firstly its rather toxic, so breathing it in is definitely not recommended. Its also explosive and evaporates at around 50C. And lastly it is around twice as heavy as air. This last point is somewhat of an issue with the passive smoothing method, as a part will smooth from the bottom up and so won't be even. On smaller models this doesn't really cause a problem, but when dealing with taller models I notice the bottom of the part looses more detail and can sometimes cause the part to warp or completely fall over, whilst layers are still visible at the top.
Ideally the vapour needs to be circulated around the part so as to get a good even covering. Something I'll work on in the future.
Another thing I noticed is that the part continues to smooth even after it has been removed from the container. I was quite happy with the result I had on a small figurine,so removed it from the container and left it on a bench to dry over night. In the morning I was shocked to find the part was far smoother than when I left it, and had lost much of the detail it showed the night before.
Now when a part is removed I put it into the freezer to halt any further smoothing.
Parts can vary on how long they need to stay in the vapour. depending on the size of the object and also the ABS. The dragon below for instance was left in for about 12 hours. Its relatively "soft" ABS, but the part was quite large. The terracotta warrior on the other hand was left in for just over 2 hours.
Another before ...