Can't get colour to stay when flattening image

I do the following with my picture:

> Adjust threshold to give me an outline
> Add gradient fill layer
> Convert fill layer to soft light so the black in the background layer is softly coloured
> Flatten image - This is where my problem is.

When I flatten the image the colour dissappears. On one image the colour just faded when I flattened it so I duplicate the fill layer so the colour was stronger & softened to the colour I wanted it when it was flattened but now I cannot for the life of me get the colour to stay whatever I do. Any ideas what's going wrong?

I managed to solve my problem, thought I'd share it incase anyone else tried using this technique & had the same problem.

In the first picture where I got it to work I added a gaussian blur to soften it up after adjusting the threshold. When I do this the colour fades when it flattens but if I have 3 fill layers it fades to the colour I want it when I flatten the image. I guess the colour can stick in the edges when I blur it but not when I don't :p