Thanks for the comment

I did the sun like this:

1. In photoshop, select a large hard brush and roughly dab in the colours of the sky. Make sure the entire sky is filled with colour. Make sure it is a light yellow where you want the sun to be.
2. On a new layer, use the circle selection tool and draw a circle a bit bigger than you want the sun to be.
3. Feather the circle to 20 pixels and fill with white.
4. Go into 'Layer Options' and give the circle an 'Outer Glow' and use the default settings.
5. Import the .PSD file into Painter and select the blender named 'Just Add Water'. You then blend all of hte hard circles of colour in the sky together, and where the yellow for the sun is, you blend outwards in a star shape.

That should work, that's what I did.