listen to my story this maybe are last chance (ffx playthrough?)

Played up until a Seymour battle many years ago

the first hour is a bit of a slog. but yeah, I doubt they've added cutscene skip.

Operearion Mi'ihen is where I'd say it picks up and doesn't look back.

Also yeah most every boss has a section where you can grind. The worst place to get stuck though is right before the 2nd Seymour fight. So I would recommend grinding up in the desert area, or even in the forest area.

1. Focusing on a small number of characters later in the game (probably including Tidus and Auron because their grids are so good, Wakka because he has high accuracy, and Yuna because she brings Shell / Protect / Nul-elements - Shell / Protect are very good in this game). Lulu's magic can easily outdamage physical damage during the first two thirds of the main story (especially if you are using elemental spells to hit weaknesses), but later on physical/strength massively outscales.
2. Trying to win the Blitzball match because you get a Strength Sphere from it (4 Strength might not sound like much, but because of how the stat scales in this game it's actually quite a bit early on). [You can also try dodging 50 lightning strikes in the 'alcove' to the east of the first part of the Thunder Plains you go through - this isn't mandatory at all, but it gets you 3 Strength Spheres as a reward, which is pretty broken at that stage of the game.]
3. Buy the Sonic Steel from O'aka in Macalania Forest for Tidus (it has First Strike on it, which combined with Flee makes you pretty much immune to dying in random battles and therefore able to explore and grab every chest easily).
4. Grind a bunch on the Highbridge (in Bevelle before the Seymour fight as mentioned above). I pretty much always do at least a little of this (n.b. the enemies are all weak to fire). The AP gains are extremely good and arguably not matched in any main story at all (because while other areas have comparable AP the enemies are more annoying).
5. Get and use Quick Hit (at the very end of Tidus' grid). Combined with Haste (also on Tidus' grid) you can be getting off 4+ basic attacks as quickly as one normal Attack without Haste, massively increasingly your effective DPS.
6. Use Summon Overdrives to blast through the hardest bosses - just bring the summon out in a random battle, get its OD gauge full then dismiss it and keep it in reserve for when you need a blast of damage. Since most bosses will need to use their turn to kill your Summon you can chain-Summon for loads of damage. [N.b. there's a second, stronger Overdrive for Valefor in Besaid Village you can pick up - try to get it before you leave).

Focusing on a small number of characters later in the game (probably including Tidus and Auron because their grids are so good, Wakka because he has high accuracy, and Yuna because she brings Shell / Protect / Nul-elements - Shell / Protect are very good in this game). Lulu's magic can easily outdamage physical damage during the first two thirds of the main story (especially if you are using elemental spells to hit weaknesses), but later on physical/strength massively outscales.

Use Summon Overdrives to blast through the hardest bosses - just bring the summon out in a random battle, get its OD gauge full then dismiss it and keep it in reserve for when you need a blast of damage. Since most bosses will need to use their turn to kill your Summon you can chain-Summon for loads of damage. [N.b. there's a second, stronger Overdrive for Valefor in Besaid Village you can pick up - try to get it before you leave).

Right before Seymour 2 is one of the best grinding spots in the main game!

It's just boring as hell and you're stuck there

Also get Kimahri on Rikku's grid for Steal and Use, then to Tidus for Haste and the Strength Spheres you gave him to have a reliable, jack of all trades party member.

I use every character in every battle so everyone gets AP

I think it'd definitely have that potential problem for folks who don't enjoy grinding