Layers in Lightroom?
I tend to have preset export functions to do exactly this sort of thing. It works for doing HDR-manual-in-Photoshop style shots too.
1. Set up a new Export setting to export a photo to a folder on the desktop. I have a "Photoshop" folder sitting there for this.
2. Open your image. Tweak so it's nice & sharp. Export it. This is your "sharp" version. If you leave the "Photoshop" folder open on your desktop, you can quickly rename it.
3. Tweak the image again in LR so you get your soft focus effect. Export that.
4. Open PS. Open "sharp", open "soft". Copy & paste one over the other and you have your two images, one as a layer, ready to be masked/erased.
I really find the export function of LR to be brilliant for this. It's so very quick to do. And LR is excellent for fast general editing.
Got a good sky in one image and a good foreground in another? Export both.
Got a great RAW capture and want to HDR it? Use the exposure slider in LR. Set to -1, export, set to 0, export, set to +1, export. Done.
With PS opening from the same place (Photoshop folder on the desktop for example), that's fast too.
File management is easy, as the export function effectively makes copies of the original. When you've finished editing, just clear out the PS folder secure in the knowledge that you haven't touched the original. If you save your finished work back to the same PS folder, you just need to Synchronise that folder in Lightroom and you can drag/drop the completed images into your file structure.
-H