Cookie-Cutter Layers
Layers can be used to create quick effective design variations on a theme. Much like a “cookie cutter”! You don’t need a computer to help you here. Simply slap your tracing paper over your initial image and re-trace the common areas, adding your design variations as you speed ahead. Using the same pen and magic markers for all your ‘cookies’, and ‘wham!’ you got multiple variations where you can quickly compare to finalize your inspiration.
I had 9 variations on this elevation!
Sketchingjourney's Blog 
Quite a choice of analogy – Cookies and decorations. Now we know.
Can you do it with CAD? But I’m sure the physical tracing works more magic.
I think every artist have their own way of dealing with their perceptions. I find my ideas are generated from variations on the themes. That is not to say that ideas cannot “drop from the sky” lol!! The bottom line is you have to work at it. That’s cookie-cutter analogy!