I have found that the trick to using the fan trick is to be quite close to the door, garage door ect., and placing the fan so that the back of the fan is near the lead or soft plastic ect and the blowing side is aimed out the door, not at the lead/plastic ect. .
So trying to be more clear about this, what you want is the airflow going into the back of the fan to be near the fumes and then have it blown out of the garage by the front of the fan. So you are exhausting the fumes. Then you can adjust the force by adjusting the speed of the fan and how close it is to the offending fumes. Works for me. Cheers.