Blend modes are something that I heavily rely on when I fine-tune my drawings in Illustrator. I’ve attached a simple example, that illustrates the difference between normal transparency and multiply in order to get a “realistic” cast shadow effect.
I know this example is a very basic one but it’ll open a complete new world of possibilities. If you are willing to implement this feature and if you need more examples just let me know and I will
prepare a more in depth explanation .