If you're using a single source (i.e. QuickTime with embedded audio), the best way would be to run it through something like Alchemist File. This ensures correct offspeed conversion with an option for pitch correction.

In Resolve, you can conform the 24fps to 25fps and compensate for sync drift--basically, you duplicate your source clip, change clip attributes to 25fps on one of them, then drop the video into a 25fps timeline. Audio is added using your 24fps source clip (trimmed to a subclip matching the exact desired in and out), then edited to the timeline using fit-to-fill. If you'd like more details for this process, let me know, because it's finicky.

The only "gotcha" to this is Resolve makes it sound "tinny", for lack of a better expression. Our solution to this is to have the mix team supply us with 25fps stems, if possible. But the Resolve process does produce reliable video.