Well it was not easy..
What I Wanted was to slow the shutter speed down during bright sun. It is easy to get blur at night. I put on a 3 stop ND Filter and a CPL in order to lower shutter speed and amount of light by 4 stops.
I then took a shot with normal exposure of my daughter, then I shot one with about a 8 second shutter of the train.
Then I took 7 shots 1 stop apart of just the building with nothing else in them.
I did HDR on the 7 shots..blended those to the way I liked them.
I then pulled the image of my daughter on and masked her off so only she showed up. I adjusted her so I had nice exposure in post.
I should ad...I used a triopod! There is no way to do this without a tripod and a shutter release cable.
The last thing to do was to bring in the blurred image, I used the "color match" tool in photoshop to get the blur to match the hdr image. Once I had the train on top I masked off the buildings and the ares I did not want to show leaving mostly the blurred area.
I then adjusted the opacity of the blurred train layer in order to get the amount of blur I wanted. The key is I wanted my daughter sharp, detail in the building behind the train, and lastly the motion of the train.
Quick how to....