Yeah it seems like every beginner thinks crossing their feet when they have back mount is a good idea. Till they get that done to them a few times. I like to take back mount off of an arm drag best. I won't always get the actual back mount though when take someone's back, sometimes I use wrestlign style breakdowns and turnovers to get to side control, or north south and go from there. One thing I do is a variation of this: http://www.youtube.com/watch?v=YMsSrh7EhwQ except sometimes I'll actually reach my hand under their arm that's closest to me into basically a half nelson (although going over the arm and head like in the video works too). And instead of hooking their far leg with my leg I'll just dump throw the leg I grabbed over to the far side and dump them to their back right into a dominant position. I also use a far side diving cradle for the same thing, finishing by letting their legs go and shifting away to nor south or side control rather than keeping them pinned. Cradles are great for getting people turned onto their back. For the latter here's a good video: http://www.youtube.com/watch?v=aiQTtjOYMvE honestly wrestling has just as good if not better techniques (or more anyway not better per se) from back control and back mount than BJJ as far as no gi grappling is concerned and adding the submission game into it isn't too difficult, especially if you delve into catch wrestling.
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Member of DaJoGen MMA school under Dave Hagen and Team Chaos fight team under Denver Mangiyatan and Chris Toquero, ran out of Zanshin Martial Arts in Salem Oregon: http://www.zanshinarts.org/Home.aspx,