Okay, so I decided to start from the beginning again. I deleted the layer I had been working on and set up a new layer for the lines. When I was happy with the lineart, I again set up a new layer for the coloring process, and put that layer below the one with the lines. I then decided where the light was coming from and coloured the pumpkinman with a medium orange or geen. Then I went for the shadows first, and then, in the end, for the highlights. I did all that with Artrage Studio pro. I then exported the painting into photoshop, removed the background with the magic eraser and added a black background layer.
I plan to use that painting as a design for Zazzle, but I will take my time and have a look for those nasty spots of colour which will have to be removed before uploading it to Zazzle.