Personally, I like the Twixtor plugin from Re:Vision FX. You can do a 29.97 interlaced to 23.976 progressive conversion, or basically anything to anything…especially slowing down footage with very effective results. Plus, it’s not that expensive in the grand scheme of things.
HOWEVER, if you’re looking to convert all of your selects to 24p before the edit, it’s going to take forever. That would probably be the best way to do it, so that your dissolves and fades would be at a proper frame rate, but again, the rendering hit will be huge.
It will still work very well to just convert your finished piece to 24p. Just be prepared for some strobing here and there (par for the 24p course). If you go the Twixtor route, I’d also recommend getting their FieldsKit deinterlacing plugin which is very inexpensive, and check out the frame rate conversion tutorials on their website.
Plus, I just like that company. Good guys.
Good luck!
Jon
TreeLine Productions
Fort Collins, CO USA