The method Alica Marie uses is basically the same method I use, except for one minor difference -- I make a duplicate layer, apply a lot of Gaussian blur (like around 25 04 35 pixels), keep the blend options at normal, then lower the Opacity or Fill sliders to around 25% or until it looks good. Then you can use the eraser to remove areas you don't want the softening.
Sometimes, for a more glowing effect, I make another duplicate copy of my original layer, set my background color to white, set my foreground color to black, then select FILTERS-DISTORT-DIFFUSE GLOW. Adjust the sliders to the correct amout or slightly more than the correct amount. Now use the FILL or OPACITY sliders to reduce the opacity to a pleasing about (about 25% to 35% depending on the look you want)
Both the above techniques were used to get a soft, slightly glowing effect on the picture of Alexa below.