This is probably the easiest thing you can do to make or break an image. The soft light technique.
1. Lets start out. Whatever you are soft lighting, open it up. I'll just use this.
2. Duplicate the layer. (Image > Duplicate) Now put the second layers mode on Soft Light.
3. Now go back to the first layer. Go to filter > blur > gaussian blur. This filter is the backbone of this tutorial. You have to play with it to make it good. Too much will spread out, too little will make it look horribly blurred. It has to be right in the middle. On this one, I used 3.0.
Thats pretty much it. This is the full final product of this image
This is a great technique that works on photos too! Try also using the select tool with some feathering for some point blurring. It's quite a useful tool
P.S - As usual this is not my original tutorial, so Credit to the Art Maker.