What if the sketch is too greasy and hairy?

If it is too greasy, you can slowly stick it to the greasy place with plasticine or steamed bread. If it is too hairy, cut the rubber into sharp corners slowly and neatly, which will be better.

The most important thing in sketch is the relationship between modeling and light and shade. The accuracy of shape grasping depends on proportion and perspective, while the relationship between light and shade depends on contrast.

When you paint, do you always feel that the dark places are not black enough? So I have been drawing on it with a pen. If I draw too much, I will see black light, which is too tired and affects the feeling of the picture. If you want to be black, you should look at the whole instead of just staring at one part and one detail.

But the painting is too rough. That's your line. The lines should be bright, smooth and concise. This needs more practice, and the lines should not be confused. In fact, sketch is formed by the regular discharge of lines. If you scribble, it looks like the whole picture is not clean and the edges are rough.