These paintings are based more on shapes than lines. Even in the Diebenkorn if you took away the lines, the figure would still be fully present, much as it is in Kim Froshin's exciting painting. An edge, rather than a line can make a more convincing object in space.
Take another look at these three images with the relationship between the figure and the ground in mind. There's a big opportunity here for defining shapes, and it can come late in the sequence of layers. Be sure to take advantage of that from time to time.
So, your homework? If you can get someone in your house to hold still, great. Otherwise, look for photos online, or in magazines that feature distinct shadows on a figure, clothed or not. Keep the drawing to a minimum. Paint shapes!