As far as I know, the Panasonic HMC-150 captures NTSC standard 30 fps (and 24 fps). I am not aware of any "overcranking" capabilities (i.e, 120+ frames per second).
When imported (Log and Capture) to FCP, the clip comes into the "browser". You select the clip and place it (or just a portion) in the Timeline. With the clip in the timeline, under Modify", select "Speed" (or command J) or Duration. Set the duration you want.
If you capture the video at 30 fps, slowing that to about 15-17 fps will be about as good as it gets. Slower than this and the movement will not be very smooth - even with Frame Blending selected.
If you are capturing FAST action, you may want to increase the shutter speed (for less single-frame blur), but this becomes problematic, too. I would recommend using a faster shutter ONLY for the fast action recording. Normal action should be recorded at 30fps. There is a "strobe" effect with increasing the shutter speed (under normal action conditions) that is very irritating. The AVCHD compression used applies a "group of frames" compression process (it is what AVCHD does), that is not too forgiving with fast action... Low-compression formats (DV, HDV, DVCAM, HDCAM, DVCPRO HD) is suggested for fast action video capture.
It would be prudent to PRACTICE with various settings on the camcorder and the video editor BEFORE you go out on a production.
I'm new to recording videos, and I just rented the Panasonic HMC150 for this weekend.
I was just wondering if slow motion is something that I should incorporate afterwards when editing my project in Final Cut Pro or something that has to be done during the filming process.