You should not have to widen the nut slots, and only adjust the truss rod if it starts buzzing. You may have to adjust the saddles a bit because the 10's are larger and will sit higher on the saddles thereby raising the action.
I had used 10's till i got my silo, and it was time for a string change...wow, it really is tougher again.
Now, on one of these truss rods, i turn clockwise to tighten it, right?