If you have a hard time imagining projected complex geometry start out layer-wise.
First the box, then the geometry you will propably get right, then easy approximizations of the complex geometry. They're propapably wrong, so draw the better version of them right over the old lines. Do that until you are happy with the result and then take the pen you want to draw the result in and follow the lines you liked.
All pictures are created in steps. No one has a 3d-renderer in his head and a plotter for a hand. Don't be afraid to draw the wrong lines, as long as you draw them in such a way that they aren't noticable on the finished image.
The better you get the closer your first lines will get to a good shape.
Also, when you begin something you will propably fail at, start out with small versions of the object and increase the size until you reach what you wanted. Small objects don't need much detail and you allow yourself to concentrate on those lines that are important. Step by step you increase the number of details. That makes the process of imagining all that detailed geometry with it's shadows and reflections easier.
* That's just the strategy I use. I don't claim that it's any good.
Vain