Is there an exercis that will reduce the amount of time I need to spend training my legs?

Try the Bulgarian split deadlift. It develops all the major muscles of your lower body - so you don;t need to bother with a clutter of leg exercises. The Instability of the exercise (because it's done while standing on one leg) calls more muscle into play as you try to stay balanced. Perform two or three sets of three to five repetitions to gain strength; do two sets of eight to 12 reps to build muscle.

Place a loaded barbell on the floor one to one-and-a-half metres in front of a bench. Facing away from the bench, place one foot on the floor so your shin touches the barbell, and rest the in-step of your other foot on the bench. Keeping most of your weight on your front leg, bend your front knee and lean forward to grab the bar with an overhand grip (palms down). This is the starting position. Lift the bar as you return to an upright stance, while keeping the other foot on the bench, then return to the starting position. Compltet your reps, then switch legs and repeat.