Following the ABS Acetone Vapor Treating videos, I saw A.Bowyers post that Dichloromethane works as a PLA solvent.
I then rushed to buy a glass pot (550ml Weck Jar) and some Dichloromethane.
Heating the bed up to roughly 100degrees with the lid on produced vapor. And about 2-3 minutes in the vapor smoothed out the part (I didn't time this, just a guess, may have been in there for longer).
The part was printed in 0.25mm layers and 0.55mm tracks, after vapor treating the part is VERY flexible (rubbery). I will see if this goes away over time.
The pinky part on top of the gear (M8 nuttrap) is from putting the part down on the heated bed after removing from the vapor. DOH! :)
UPDATE: After about 18 hours, the part is back to 'almost' being solid again. Just a slight amount of flex. Presumably if you left it in for only a minute, this would take less time to solidify. I did try the small gear for a few seconds by just lowering it into the vapor, there was noticable difference to the layers, but the part remained solid.
Be very careful when using this chemical. See http://en.wikipedia.org/wiki/Dichloromethane
Always use with an open window / adequette ventilation. Or use outside if possible.
When lifting the lid of the pot, I held my breath and kept my distance. If possible, make a scoop/hook to remove parts to lessen any exposure of the vapor with your skin.
This chemical has been linked to cancer of the lungs, liver, and pancreas in laboratory animals.