There are some handy life drawing sites out there, one of which is https://artists.pixelovely.com/. You can set it to give you gesture exercises (where you get 30-60 seconds per drawing) which is great for improving your focus and getting down the main shapes. In the absence of having somebody naked to hand, I’m doing about half an hour every morning to keep my practice up. Another blog I follow is https://www.johnmuirlaws.com/blog. He’s a wildlife artist and there are some excellent tutorials on there. One of his suggestions is to draw a box around the main body of the animal – it’s kind of an alternative to measuring out the scale. I’ve been using it with life drawing and it not only helps but is so much more enjoyable than holding your pencil out, which takes me back to school art classes and not in a good way. You can then follow that with the points system (where you map out the points on the body). Here’s a pic from this morning using that method.