What are some of the quickest ways to build momentum towards a signature move? Do you have to vary your attacks or anything? A series of strikes will build it up but it just seems to take forever compared to some videos I've seen of matches.
Running strikes. Running grapples. varied attacks. quick grapple moves. don't repeat moves all the time. also reverse moves where you can. if you manage to knock down your opponent for a bit, taunt them.
If you really want to get in depth, the create-a-moveset option usually has the amount of momentum that each move delivers.
Regarding the videos, remember that some people do adjust their settings to make it suit them