Design hand Sketch skill is an ultimate tool for a pro designer. In a hand sketch, you can create multiple design concepts in minutes. Going directly to a 3D CAID tool is a massive mistake. Creating a concept on a 3D CAID will take you hours if not days. That will focus your attention on the one concept took you so long to create, and will disable from your imagination the many other options not yet perceived.
Here are some Design Sketch videos we collected for you from YouTube: