I've been recently teaching online. The current exercises I've been working with my students on are value studies. We've done the typical still live studies, but last week I made it a bit more interesting and chose one of Rembrandt's portraits.
These are only small quick little studies, with the aim being only to capture the essentials of the image, with an emphasis on the values while ignoring the details
Losing ourselves in the details is something that we all do as beginners. The details are the "false friends" that lead you astray. They are like eating your sweet desserts before your main course. Consume those first and you'll never get to the real substance that gives sustenance to your image.
"Rembrandt Study", Leo Plaw, 12 x 17cm, acrylic on card