Slow Motion Effect using DSLR camera

(it's not test-proof yet, but may help)

First of all, relationship between shutter speed and smoothness.
For sports photos, the shutter speed is set to very fast (1/2000 s) to freeze the motion.
In compensation of light, you need a lens with big aperture.
more details on exposure, pls read here.

When you film using a fast shutter speed, it won't slow it down but the movement of object is smoother.
see the difference here

You could film using DSLR camers in the rate of 50 frames per second. (or 60fps for NTSC format).
By conforming it to half (25fps) using Cinema Tools (a component in FCP), you will actully slow it down and obtain a smooth slow motion effect.
Keep the original file before you conform it.
See the detail here.

To slow it down further, use Aftereffects. Be patient.
A very good tutorial on time remapping (0:00 -8:46)and speed change (8:46- end).

For super slow smooth effect, sorry, you have to pay for it.
A super example.

This plugin Twixtor seems work well with simple backgroud.
you can download the trial version.
Fair result with messy background.

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