Have you tried the following free site: http://sketchupforwoodworkers.com

It's what got me going. I use a combination of analog and digital for design tasks. I do my rough forms in a sketchbook, and refine the idea into isometrics on paper. It's not until I'm happy with the overall design that I turn to Sketchup. It's often just to get an idea of how everything will come together and to ensure that I don't run into any interference issues.

I'm actually writing a design series and will jump into Sketchup at some point: http://bloodsweatsawdust.com/2015/03...-introduction/