@Harmony Steel I really suggest picking up Joe Weatherlies book the weatherly guide to drawing animals, and you can also learn a lot from his other available books, animal essence, animal nature, and sketchbook volume 1. I have talked to him and he has recommended the classic Ellenberger animal anatomy for artists book. It has been a great resource for me to get started learning animal anatomy. I dont have this, but if you have the money, get a model from juns anatomy, they are extremely useful for studying animal anatomy, and the surface forms.

I think you need to study kangaroo anatomy and details, and draw them from life at the zoo, and then make a YouTube video drawing an awesome kangaroo from memory