another fun thing to practice is to go to public places, sit down with your sketchbook, and doodle the people who walk past. what really helped me was to go to places like gyms for muscular types, and parks or zoos for normal types. for the big types I just sit down in a restaraunt. getting in to most of these places either doesn't cost much or is free. And most won't care if you loiter as long as you bribe them with sketches or buy something there. It's also a great way to learn how fabrics move. it doesn't matter if you get in a whole lot of detail either, just a rough sketch of what it generally looks like is enough. and focus on one peice of fabric, or one body part that seems like you've never drawn that before. take it slow, and don't rush. there's lots of poeple. I like going to the restaraunts myself, I can get a drink, sit down, and watch the children, or the adluts in their natural environments. also, drawing fat rolls may not seem like the prettiest art, but it helps alot actually. especially with the female body. if you learn how to draw extreme curves, you can tone them down a bit and make them very pretty. and no harm meant to anyone who is heavyset, most of my family and my friends are very big, so I sympathize with that problem.