Before you can master your full Chaturanga, you've got to master your half Chaturanga. Half Chaturanga push ups are the best way I've found to build the strength to get to full. So once you've used this tutorial to nail down your alignment, I recommend that you do at least 3 half chaturanga push ups every time you do a sun salutation. Once those start to feel easy, you're ready to start trying the full (knees-up) version of the pose!