In 1/10 Tc we put our esc's in water tight box's so no water at all can get in there. But yes you need a fan in there really with a few small holes to let fresh air in.
Regards to motors u just seal up both the endplates and put loads of sealent/blu-tack around the sensor lead plug on the motor.
Yes, non sensored motors are alot more reliable in the wet as... in sensored motors the main thing is to make sure the sensors dont get wet. But if its sensorless u shouldnt have a problem.
