Hello there! This is a bit tricky to explain, but in general, there are two important things to keep in mind when shading organic forms. The first is the form itself. You already have a good understanding of the basic forms, but you’re not fully considering the twists and turns of the tentacles. Ideally, you want to keep those rotations in mind as well. The second is the direction of the light. The specific hatching technique you choose will usually work as long as you’re thinking about those two things. It’s also important to remember that your hatching should follow the forms. Doing so helps reinforce the volume and prevents the shapes from feeling flat. I included three examples that I’m familiar with, or at least techniques I’ve used myself from time to time when shading with hatching. Another approach is to use only a few lines to suggest texture, or to place the texture primarily in the transition between light and shadow. Keeping most of the texture in those areas gives you much better control and helps prevent the drawing from becoming covered in texture everywhere. Hope this helps!
