[Athrax]

Hi! 
I've recently had to clean up a large number of plastic parts that were more or less
soaked with old, dirty, crusty mineral oil residue. I've given them all a thorough soak
in White Spirit. So far so good. Now the parts are clean...and are strongly smelling
of the solvent, which refuses to dry up quite as fast as I'd like it to. 
 
Is there an 'intermediate' and easily obtainable solvent that will dissolve/dilute/mix
with the oil-contaminated white spirit, and which itself will mix with soapy water to
clean up afterwards?

My gut instinct tells me to look among the alcoholes, perhaps isopropanol or (more
easily available for me) ethanol, as it will both dissolve polar and nonpolar compounds.
But before I dip into my chem stores and potentially end up wasting valueable
resources, I thought I'd ask here.

Best regards,
-Athrax

[wildfyr]

Paint thinner (aka toluene and xylene) will dissolve white spirits, then are rather volatile and should evaporate on their own. Also, cheap at the hardware store.

[P]

What is the plastic?

As wildfyr suggests - other solvents like toluene would work, but they might dissolve the plastic. Acetone will probably work too and evaporates very quickly. Again - it might dissolve the plastic that you are cleaning though, so it will depend on what you are trying to clean.  What about IPA? It isn't usually so attacking to many plastics as toluene or acetone but should cut though the spirits.

[Arkcon]

Athrax:, you have good instincts for the cleanup, but you may be expecting too much from a soak.  You've gotten the oil off with the white spirit, now you have the "white spirit smell" even after "some" evaporating.  Isopropanol is a good way to get residual non-polar solvent off, and it evaporates pretty quickly too.  At this point, a wash with soapy water, a thorough rinse and a good drying with lots of ventilation should help too.

Now do the pieces still smell?  Yes?  Now check your hands, do they smell faintly?  Leave the room, and smell your shirt, is there a faint smell.  Take the pieces to another room and wait -- where is there a faint smell -- the new room coming from the pieces, or the air and surfaces in the previous, now empty of pieces, room?  See, in these cases, no amount of cleaning, with newer and more esoteric solvents is what's needed, only time, ventilation, and an understanding of how sensitive our noes are to traces of certain volatile organics.