Thumbnail sketches are small drawings which help plan your larger, finished, works. There's noting 'finished' about them, and they are generally thrown away once you begin the final piece. So why not use 3D software to help generate some ideas? As far as 3D software goes, Sketchup is very basic and straightforward. Even if you aren't interested in making complex models in 3D, doing a quick block-in of your scene and then moving around it in 3D space can help you select dramatic camera angles.
The goal of thumbnail sketching is to generate a large variety of design possibilities in a short amount of time. With this goal inmind, it's not 'cheating' to take a non-traditional approach. This video shows how to "built" your thumbnail sketches instead of simply drawing them. Using robots as subject matter, we'll first build a set of modular components, and then mix and match them to create a large variety of robot designs.
Sometimes the digital workflow will behave completely counter to the way you learned to draw with a pencil and paper. Though it might seem foreign and strange, I encourage you to embrace these new opportunities! In this video I'll show how to iterate through a set of thumbnails by chopping them up into pieces, mixing, matching, and contorting them. Though it's not much like traditional 'drawing', it's a lot of fun and can be a huge time-saver.
The goal of making thumbnail sketches is speed. You're trying to get a lot of ideas onto the page as quickly as possible. This video explores the concept of symmetrical thumbnail designs. Specifically, it offers a single-button solution to create these horizontally mirrored drawings. Photoshop actions can be a huge time-saver if you know how to use them - and this 'mirror action' is no exception.