Cezanne said that everything in nature is made up of spheres, cylinders and cones. So if you can paint those then you should be able to paint anything in nature. When using watercolour, we normally model form and volume by applying successive layers of paint. Take a look at the examples above and work out how you would tackle them. Try and paint the doughnut (toroid) shape or the bubble.
I painted all these using brush, paint, water and my new device in just one single pass. I paint in 3D. I will be explaining how you can do this too in some tutorials that I am currently preparing to publish here on the internet.
If you want to make your own device for as little as the cost of a half pan of watercolour paint, check out my New Watercolour Innovation.
I'm hoping to have the tutorials ready soon so check back occassionally. Oh! by the way the red/yellow sphere was painted with alizarin crimson and raw sienna both on the brush at the same time. I'll also show you how you can paint the most convincing wet-in-wet rainbow with four colours on your brush all at the same time. Impossible? No. Not anymore.