I'm just commenting here for now so that I remember to come back later today when I have free time and gives you some pointers.

Simple but effective method that I use:

Start with your regular lineart, draw it like you've always done. When the lineart is finished, you add a new layer and on that layer you are gonna do shading (different tones of grey/black). Shade in around the lineart, shade, shade, shade a lot. After that, add highlights, using the eraser tool, on the same layer. When you have done all of this you add another new layer and start to colourize with base colours. You don't need to use different shades and highlights of colours because you have already done all that in the other layer. Last step is to delete the first layer where your lineart is.

Just a suggestion, I do this all the time (: I only use Sketchbook Pro though...

Just wanted to let you know I haven't forgotten about this, I just had a busy day and am trying to get the hang of a new laptop. Once I'm settled in I will put together a little shading and light source lesson for you which should help clarify how to place highlights and shadows when you paint.

Ok so I've taken a look through one of my favourite art books for you for the pages that deal with the basics of shading. The book is called 'The Complete Book of Drawing: Essential Skills for Every Artist' by Barrington Barber. It is a fantastic reference and I strongly advise any artist to buy it or at the very least, get a copy from your local library.








The image above does not directly involve how shadows work, but I have included it because it shows several different ways of laying down colour. Some of these are useful for showing fur and other textures, it could be useful when you work with deer.

Pro tip: Do not draw from your imagination for this! You need to draw from life for this lesson if you want to really understand how to shade realistically. Get an apple and set it up near a lamp (or flashlight). Move the light around the apple and see how moving the light source changes how it looks; focus on how strong (dark) the shadows are and where on the apple they are. Don't forget the cast shadow! A cast shadow is any shadow that an object casts onto another object. You are most likely to see them on the table underneath your apple. Now that you have your apple and lamp set up, get a soft pencil and some paper (and an eraser) and start drawing what your apple looks like. Draw what you see, not what you think the apple should look like. Once you get comfortable, try changing the light source.

Once you have the fundamental knowledge of how light sources and shadows work, you can move onto applying that knowledge to shapes other than the apple/sphere.