25 fps smooth speed up

Hi,

have a simple question…
I’m filming with Canon 5dii at 25 fps. Is there a way to speed it up in post, and make it look smooth ? I’ve tried to do that with very slow horizontal panning shot, and it looks choppy. Tried to better it with directional blur and optical flow, no much difference.
Perhaps I should convert sequence to 50 fps, and try again ?
Any thoughts ?
Thank you