Step by Step breakdown of what Brock Lesnar did to shut down Frank Mir's half guard at UFC 100: http://www.grapplearts.com/2009/07/brock-lesnar-vs-frank-mir-how-to.htm
This is an excerpt http://www.grapplearts.com/Half-Guard-Sweeps-Info.php showing a great drill to improve your bottom half guard position for Brazlian Jiu-Jitsu and Submission Grappling
Stephan Kesting (http://www.beginningBJJ.com) talks about how the top mixed martial art fighters, coaches and teams include Brazilian jiu-jitsu (BJJ), wrestling and striking in their MMA training.