This may sound strange, but in a pinch when shadowing the form (or when traveling), you can mark the corners of an upside down equilateral triangle with 8" base and use that to keep your range in check (drop the bottom corner about 5 inches extra). It won't train the contact or navigating around the elbows of the dummy but it will help keep your range in check. White boards or small bits of painter's tape are useful for this. An actual dummy is always better!
Mook Yan Jong is a Wing Chun core form.
You can find it referenced in most Wing Chun study material.
A good exercise to start on is the Man and Wu combo hand position and then work some of your moves in off that.
Im sure you know not everything goes together.
Have fun