I have never fished for musky. I do fish Green River Lake very often and average about 4-5 musky a year. I had one on last week that was in 2-3 ft. of water right at the base of a stump. It broke me off but I could tell it was decent in size. I was pitchin a worm when it bit.
From my experience if he wants to catch a musky on Green River Lake now is the time. In the fall I have caught the majority of them in the back of coves where shad is present or on a flat that has wood. I have had them to bite in very shallow water but typically when that happens it is a smaller fish 35" or less. The better bites come in water deeper than 5 ft. Most of the time I catch them while fishing a buzzbait,spinnerbait or square bill crank bait.
In the fall is when I have the most bites. In the spring I do not catch as many but the quality of size is better. If you think he has the fever now just wait until a 40" fish blows up on a buzzbait. It sounds like a concrete block fell off a cliff into the water.