Step 20: Use the curved line on the left as a guide to draw the wolf's fluffy tail. Just like the legs, first lightly sketch the shape of the tail around the guide. Then, when you get the shape right, darken the lines. Draw the shape of the wolf's tail using longer strokes to create a bushy texture.
Step 21: For a cleaner look, erase as much as you can of the initial guide lines. Don't worry about erasing all of the guides. It's okay to leave some behind. Re-draw any final sketch lines you may have accidentally erased.
Final Step: Add some shading to your running wolf drawing to give it more dimension and volume. Pick the direction of the light source when shading so that the shadows are consistent with it. Vary the pressure on your pencil to get different degrees of tonal value. You can actually stop here for an all-white wolf.
Add a cast shadow underneath to emphasize that three of the wolf's legs are off the ground.
You can add even more value to your wolf drawing for extra detail. Use a medium value for the head but leave an area around the eyes blank. The lower half of the head is pretty white, so leave that section blank. Shade the bridge of the nose lightly. Darken the shadows a bit too. For a more detailed guide on how to shade, check out this tutorial: How to shade.
As you add the value to the body, use strokes that go in the general direction of the fur. Separate each individual stroke a bit so that the white of the paper comes through and emphasizes the fur-like texture. Don't worry about shading too smoothly. The rough value gives the wolf's coat a furry texture.
If you make the value on the wolf's body as dark as the shadows, make the shadows darker so they stand out. Shading can be time-consuming, so be patient and take breaks. Continue to add value to your drawing until you're happy with the level of darkness. It's always a good idea to use reference as you draw. Remember to pause the video to draw at your own pace.