If you have a freezer that can reach -20 degrees C then use it. An acetone/dry ice bath would definitely work, but it would be unnecessary, and certainly more of a hassle. You could precipitate the DMT out of the solution in a shorter amount of time though.
The freezer precipitation works just fine, make sure its a cold freezer, stick a thermometer in there if you have one, and wait ~12hr.
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If you want to skip the process entirely I would recommend a FASI precipitation. It is superior.
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