23.98 to 29.97 via Compressor:
1. Drop clips you want to convert into Compressor
2. In Compressor, select your video then right click and choose NEW TARGET WITH SETTING > APPLE > FORMATS > QUICKTIME > APPLE PRORES 422 (HQ). Or pick whatever codec you like to work with.
3. Click on that newly created compression setting to open it in the Inspector window. Click the Encoder tab. Click the Video: (Settings…) button. Make the frame rate 29.97. Check the interlaced box. Set it's drop down menu to Bottom field first. Click OK.
4. Click the Frame Controls tab. Set Frame Controls to On. Set Output Fields to Bottom first. Leave Deinterlace on Fast. Leave Adaptive Details checked. Leave Rate Conversion set to Fast. Leave the Set Duration to: on 100% and make sure it's radio button is selected and NOT the "so source frames play at 29.97 fps" button.
5. Make changes to the Filters or Geometry sections as needed. Those settings listed above are the ones critical to getting the proper 3:2 pulldown added.
6. Submit the compression, then bring the resulting video back into Final Cut Pro. Place it in a 29.97 timeline and make sure you watch it on an NTSC monitor to verify that it looks good. If you step through it frame-by-frame you should see the familiar pattern of 2 split/interlaced frames followed by 3 whole frames. This is a very important step. I tried many solutions that looked OK playing back on the computer monitor, but looked terrible on the NTSC monitor.