Once you have the reflection layer all snazzed up the way you want, duplicate that layer above the reflection layer, blur the dup'ed layer (radius 2-3 pixels, or to taste) and then lower the opacity of that layer. You can also create a gradient layer mask so that the reflection is sharper right near the actual car, blurring as you move away from the car. I used the "Soft Light" blend mode on the reflection layers to composite it into the background plate.
I also added a Distort>Ripple or some similar distortion to slightly deform the reflection as if the reflection were being seen in a wet surface on slightly uneven pavement. If it is not terribly obvious, which it is, I just cloned the pavement into the extended canvas area to get more parking lot. My image was sort of a proof of concept - if you take your time, you can make it more convincing. As you can probably tell, I only "reflected" the car, not the entire scene. Totally a judgement call.
have fun!
Kirk