After Effects - Learning Masking

Hi everyone! I was wondering if anyone knows of any course or tutorial or something regarding everything to know about masking on After Effects. I've looked and so far I can't seem to find anything that really goes in depth very much. I have used masking before, but it's been awhile, so while I do still know how to create and track a mask, it's more or less the bare minimum. For example, I don't remember how to draw something in Photoshop and then import it as a mask in After Effects. I also can't remember how to move the mask around the footage. Any help you can offer related to those topics and others is much appreciated! Thank you!