Try this variation,
Against right lunge punch.
When you step in block the attack then pull your opponents head to your right shoulder. If you can, apply pressure with your finger to the pressure point under his left ear lobe. Remember to pull sideways not forward or back. From there bring your other hand up to tightly come under his chin. You want to kind of choke him as you turn around. While he is off balance point the elbow of the choking arm up and with the other hand push into his lower back. He should then drop to the floor.
Other way to break the balance is when blocking attacker's arm, spin into his elbow. What I mean is you push his arm down and position the elbow on your chest or whatever then push into it with your body while bending it back with your right arm.
Things to remember are always keeping your opponent off balance. Soon as his foot is off the ground throw! Secondly remember the principle of the neck and lower back. If you push the chin up and down like dunking a basketball while pushing his lower back you will force his feet to go out from under him.
If he is very strong then you can kick his leg out as you throw or go into a choke or you can hold on tight and throw your body in front of him (sutemi waza). Once taken down you can continue your choke.