Remind me to see if you've got anything for long-ranged fighters later... but close range, there's usually a moment where they're open enough, and that's when they're aiming for you. If you can avoid or take that first hit, try to get under their guard and aim where you can. Abdomen, stomach, chest, below the belt, under the chin... they're all good spots to either get your opponent down or further away from you.