I consider myself to be somewhere between and a beginner and advanced user. Something I struggle with is perfectly cutting out an image, most likely a human, so that the hair looks natural and not cut out. By using the select and mask took, you can highlight the area in which you would like to cut out and use the sliders (feather, smooth, contrast, soft edges, etc) to make your selection seem less cut and jagged. I think I prefer the black background over the onion skin background as you can see more of the selected areas. I learned a lot from this tutorial and it is perfect for learning how to more carefully make a selection.
“Photoshop Training Channel.” How to Cut Out ANYTHING in Photoshop [SELECT and MASK Crash Course], 5 Sept. 2018, www.youtube.com/watch?v=0qcWeuWCkJ4&feature=youtu.be.
This is a great selection tutorial for masks!