Educomp smartclass CTS has a large number of 'Diagram Makers', modules that help teachers show students how to draw diagrams step-by-step. These are available for all science subjects, and Geography in classes 6 to 12.
Here is an example:
Look for the relevant diagrams in the Smartclass recommended lesson plans. Make sure students draw the diagram by following the steps shown in the Diagram Maker.
Here is another example. "Transverse section of a nerve". You can see how the complicated diagram is broken down step by step and becomes easy for the student to follow!
Some teachers have pointed out that many diagram makers are very slow, and take a long time to cover in the classroom. My suggestion is that show a selected set of diagrams in class, the really complicated ones. In case you find that students have difficulty with any diagram, then go over that diagram in class.
Finally, remember that these diagrams were made because students complained that teachers go too fast when drawing diagrams in the class! So what is important is that students learn to draw the diagrams, not the speed of the diagram maker.