Jumping in here to take over from Tofu.

To your first question, keep in mind that everything we do in this course is an exercise. It is not uncommon that you'll find approaching something in the manner described in the lessons will result in little blunders and mistakes due to you not yet being at a level of skill that would allow you to execute those things consistently. That doesn't mean it's wrong - it simply means that, being exercises, you're practicing the things that need improvement. That's the only way they improve - though many students will feel tempted to change the nature of the task to something they're already better able to accomplish, but that of course would not really yield much in the way of growth.

And as to your second question, hair and fur both are made up of individual strands, but they clump together to create larger masses. These are the forms we focus on, in terms of having them cast shadows upon one another. You can generally work from big to small - focusing on the major groupings/massings of hair or fur to put down your major shadows, then finding spots where you can imply some smaller groupings and individual strands - though this last part would be quite minimal.

One of the general skills we do develop in this course is communication - it's like we're the only ones with access to the reference image, and we have to share that information with someone else, only through what we draw ourselves. That requires us to interpret what we're seeing, and to strip it down into what is most important - treating hair and fur as clumps in this manner is an example of this. We're communicating what's there, not with hyper accuracy, but with a focus on simply conveying that information to the viewer.