^It's super easy to have all the points you need by the end of Chapter 2 and you'll never have to touch it again. You need 400 points for one company by the time you go to the Calm Lands in Chapter 5 to get an episode complete for 100% completion. I hated that side quest too but honestly, when you finish up in an area or even as you're going through it you can just find the people and it's not too bothersome.
Here's the FAQ (I'm sure you knew that already).
MASCOT DRESSPHERE BITCHES. Episode complete everywhere. Also it's possible to collect more than one dressphere which is freaking me out a bit. Because the creature creator drops dresspheres I have the number "2" sitting on the Festivalist dressphere XD.
I wanted to get Mascot before going into the Via Infinito. I've officially done everything else (levelling up experiment and killing it, angra mainyu etc... all at level 50. Was a bit of a grind but it was challenging so it was fun!). I'm thinking I'll collect the last Crimson spheres from the early via infinito so that I can completely round off Mushroom Rock so that the Infinito really is the absolute last thing I need to do.
I've got to say I'm just loving this game right now. X-2 probably takes the same amount of time to platinum as X does, but it's less noticeable because it's just not grindy. I mean the infinito is but I did it on PS2 and didn't get bored... we'll see how I fare with it these days. Of course after all this I've got Last Mission which takes about 10 hours.
Quite honestly the most boring thing I've done is find the amazing chocobo (send chocobos out at each level, fight 7 battles, level them up one, fight 7 battles etc until four of them arel level 5 so you can unlock a dungeon) and that's only because catching chocobos that are capable of levelling up to level 5 is a pain in the ass. All in that whole sidequest (from catching chocobos to finding the actual amazing chocobo) took about 3 or 4 hours though, so it wasn't too bad. This is also considering that I fucked up and had to grind for greens.
I can't see exact completion percentages but I should be on track based on what I've done (I'm out of sequence for all the guides because of the order I wanted to do shit in Chapter 5).
The main grindy thing I've got to do is oversoul all the fiends, but I've done all the dungeons up to now so the only one left I have to kill outside of the Via Infinito is Azi Dahaka. I looked into the creature creator method of doing things. I've decided I'm going to do Via Infinito first since you can return there after beating Trema anyway. I don't like the idea of going into the final dungeon to get to Azi (like a pubic hair away from the point of no return) because I just prefer doing final dungeons without interruptions for the story, but the Creature Creator way of encountering him seems like an absolute chore. You can also lock yourself out of it by levelling up too high (certain cups require you to unlock full field tales, you can only unlock those by levelling the fiends up, fiends caught are at your current level so if you're above say lv. 93 you can't do it and also it'd be super grindy) so I might just forget it and do it the old fashioned way.