I'll leave the contentious issue of how full to fill to someone else to deal with.

You can either push or pull air through the grain.  Normally, you simply turn the fan around to make it go the other way.  Fans are slightly more efficient pushing then pulling.  This also captures the heat from the motor to reduce the humidity of the air slightly.  

If you are pushing air, you want to check at the top.  Either check the grain moisture or check the temp and humidity of the air coming out.  If you are pulling air, the only real choice is to monitor the air coming out. 

If the corn is really only 16%, it won't take any special effort to dry it down. Use the fans to manage temperature and you will probably achieve enough drying accidentally to get to 15.  

It is my opinion that the best way to manage temperature is to get the corn as cold as you possibly can as soon as you possibly can, and then leave it that way.  

Your mileage may vary.  I am no expert on storing grain, so do not take my advice as anything other then someone's opinion.