I recommend going heavy with short reps. Like the 6 rep range. Pick whatever you like from this list and go for it. You can google them if you dont know what they are. He will get strong as hell and put on some mass.

Standard barbell deadlifts
Romanian deadlifts
Barbell back squats
Barbell front squats
Barbell overhead squats
Dumbbell lunges (walking or standing)
Dumbbell step-ups
Barbell clean & presses
One arm snatches
One arm swings
Two arm swings
Barbell high pulls
Barbell or dumbbell incline or flat bench presses
Dips
Push-ups variations
Pronated grip pull-ups
Supinated grip chin-ups
Lat pulldowns (supinated, pronated, or neutral grips)
Barbell bent over rows
One arm dumbbell rows
Renegade dumbbell rows
Seated horizontal cable rows
Overhead barbell or dumbbell presses
Dumbbell squat & presses