You can accelerate the evaporation more safely by putting the solvent-wet changa in a dish that covers a pan filled with hot water.  Boil the water in advance, before placing the solvent containing changa over it (in fact keep it well away from the fire).

With accelerated evaporation, it is even more important to do this in a well ventilated space.  Outside is the best place.  The ventilation will also help to further accelerate the evaporation.