I think I always run both tires in the "Forward >" direction, though some people turn the tread in the rear around. I don't think it makes much difference
As for the mix - on hard courses with grass run the Jet in the rear and the Mud in the front. I do a lot of riding in the winter, and on snow and ice I run the Mud in the rear and the Jet in the front. This might work well in sand and deep mud too. Traction in the back and a front wheel that slices through the glop. On average courses with a mix of everything you can't really beat Muds front and back. Good luck! Hope this helps, for what it's worth ... whatever you do, I think you'll find that the Mud2 is the best clincher out there. Even though I now race on tubulars I always bring a set of Muds just in case the course goes deep!