Club trajectory is severely affected on downhill shots. Take a more lofted club, adjust your weight and chase your swing down the hill
Start your practice session by picking a close target that you know the distance to and hit little wedges that land at the spot, this will start you off with solid impact and contact as well as help your short game
Do not always use a lob wedge to chip around the green, sometimes using a hybrid with a putting stroke will provide more control and creativity