Average blur to create a soft background

Open portrait image in photoshop

Duplicate layer

filter-blur-average (to create a layer with average of colours in photo)

Duplicate background layer again and put on top

Use Object selection tool and click select subject in options and then select mask workspace in options.

View on layers in properties panel so layer below shows through.

In properties at bottom output to new layer with layer mask and click ok.

Select a black brush with low opacity say 30% and paint over background so that some shows through the average colour so creating a soft blurred background.