Simply use the brush tool to apply light or heavy amounts of blur effect to any portion of your photo - foreground, background and mid-ground.

Adjust the brush size and intensity.
And select from a number of brush shapes from the editor for fine picture control.

Vasoline Lens is inspired by soft focus, a lens flaw, in which the lens forms images that are blurred. To recreate this effect people would smear petroleum jelly on a clear filter or on the front element or even the back element of the lens itself. Messy times!