How would you BIL know about the deer activity unless you were telling him? He might feel as if you were inviting him over.

All deer activity stops when he shows up? Then go out with him and instruct him on how to locate sign, and stand placement. Stay with him....in the tree next to him.... and teach him how to sit still, let him know what he is doing wrong. let him know what he is doing right.

Teach him scent control.

I hope you find something that helps. Good luck.

FOOLPROOF?
Never underestimate the power of a fool!

What if the "Hokey Pokey" really is what it's all about?