Modified contour means, very simply, that you can look at your paper and use your good hand, but stay connected to seeing through touch. So, you're looking at the model or your object from nature, and you see that a line travels down and over. And as it turns and goes over...you've lost your place. So you stop drawing, look at the model, look at your paper. Put your hand where you want it to go, start drawing without looking at the paper again. You've lost your place again. You look at your paper again. Then go back to looking at the paper more while you're drawing. The reason being that if you're looking at the paper more than the model, it stops the flow of touching over and around. This quote by Auguste Rodin says it beautifully...
"Not once in describing the shape of that mass did I shift my eyes from the model. Why? Because I wanted to be sure that nothing evaded my grasp of it. Not a thought about the technical problem of representing it on paper could be allowed to arrest the flow of my feelings about it, from my eye to my hand. The moment I drop my eyes that flow stops."
You see you get worried about the product. This drawing is a by-product of your investigation. It's not even the point. What is important is that your hand has been activated. That it's really feeling like it's touching its lover. And that everything is being engaged. When I look at a bird or a dog, I think as if I was touching the bird, or the dog. That's what I want your lines to do. That's why you're learning this. To learn to work for a discovery and not a result.
So, do a twenty-minute pose. And you can look. You can use your good hand, but don't squeeze the tool. Just relax. And when you see that you're traveling downhill, let your arm go. And when you've lost your place -- you feel like you've fallen off the page and you can't see where you're going -- stop, look where you are on your page, place yourself, and begin again. Look at the model. Just don't look at the page when you're drawing the model. There's no information on your paper. Now, this is like a sensitive recording of your attention span. The same way that an electrocardiodiagram is of your heartbeat.