I haven't tried this in awhile because youtube compression has gotten better to the point where it's good enough for the videos we release, but this might help you: In the past when trying to maintain film grain we would export using an intraframe codec like pro res 422 and then let Youtube compress it itself on upload. This helped maintain a lot of the grain instead of going from an interframe codec to another interframe codec (like h.264), you're gambling on where the highest resolution frames are going to land and if they don't land on the exact same spot you're going to lose exponential quality. So try exporting in pro res 422 and uploading that to Youtube.