Bracketing is an option, but it also leaves you three or five times as many pictures on your memory card and slows down post processing. Also, you simply might forget to bracket or find out after that a picture you wanted didn't expose as well as you had hoped. The good news is that you can do 'that bracketing thing' even with a single image and here's how.
I usually start with the Gradient tool (shortcut key G, simple black to white used) that in the first instance blends the two images nicely. Following that, select the brush tool (B) and continue to paint on the mask (with a black or white brush selected) to further finesse the exposed parts of the top/bottom image. And why this is superior to using the brush in Lightroom is that the brush can be altered in so many ways and opacity can be set anywhere between 0-100% so you have huge amounts of control when blending the two images.
It's all rather simple and the screengrab below shows the two images and the layer mask so you see there's nothing really to it. And remember, because it is the same image, they are perfectly aligned so you don't even have to worry about that either (if they were a bracketed set, you can use auto-align in the Edit drop down menu which does a good job).
When opening up the shadows (even to 100) is not enough and the shapes are too complex for a simple graduated filter, this is a powerful tool for recovering images that on first viewing look like basket cases. There are of course other ways to do the same thing, after all, you are only manipulating the data that is already contained in the file, but this avoids problems you can get around glowing edges when selections are made and more complex uses of layer masks.
Given how difficult the conditions were in Chipping Norton that morning, my final haul of shots look pretty terrific, in no small part due to this technique. Repeating what I have shown above, here again is the 'after' shot.