I have quite a bit of old naphtha poured into bottles after my freeze precipitations (Couple water bottles full). I assume there could be quite a bit of DMT still left in this naphtha. What would be a good way to extract any remnants?

A friend had the same, about 1 liter of naphtha - he was happily surprised when after more than a week in a very cold freezer more xtals had crashed out.
Use for the next extraction...
Evapping large volumes of solvent is not desirable - try an extended freeze on the combined pulls.
Best,
L

As well as lowering temperature to decrease the solvents ability to dissolve, as will increasing saturation via evaporation.
It is good practice to evaporate off some of the naphtha prior to freeze precipitation as this will "super saturate" thus "pushing" out the product upon temperature drop. This method of evaporating off a volume of solvent prior to temp drop can be done on previously used solvent...
One can even evaporate off the solvent entirely but it is not needed.

Please only evaporate solvents outside. There are very real negative effects on health from solvent inhalation!
...not to mention the flammable/explosive nature of solvents.