I assume you can do the stage portion without losing 4 lives. The only thing to keep in mind for the last fairy is that if you're invincible when it dies (either from a bomb or death) it will drop a bomb and not a 1-up. So make sure to either bomb in the beginning or just not die. It's very simple left/right movement anyway (or, if you're scared of muh density, the safespot in the left corner).
Keine's first and third spell cards are essentially static, due to the fact that the bullets are a mix of static/aimed; and it's not a very difficult pattern to navigate in either case. The second spell isn't very difficult to just capture either, but it may require some practice. The easiest height is probably somewhere in the middle of the ball at the top and the bottom. With some practice you should be able to reliably capture that one too.
Now for Mokou: Iwakasa, Flying Phoenix, Forgiving Shrine, Xu-fu, Honest Man's Death, Fujiyama Vulcano and Hourai Doll are all really easy if you know how to approach them. The main problem I've seen people have is that they have no idea what they are doing, flailing around and then chain dying on Fujiyama. For Iwakasa, Fujiyama and Hourai Doll in particular I suggest looking at someone better than you and how they've handled the attack. There's likely a few good enough replays on Gensokyo.org for that. Now then, you will still need a general approach to some other attacks, like Flying Phoenix and Woo.
This is a very easy, but reliable approach to Flying Phoenix. The movement can be repeated until the spell times out, but with Border team it won't take much longer than with Youmu. This is something you can practice in spell practice until you get it down. Woo is much harder because it's quite random to boot. Most people misdirect Mokou's aimed shots by going above her (again, a replay how this is done will help), and it's likely the easiest way. Phoenix tail is just dodging, so get used to how the hitbox on the small fire balls works and then good luck. Possessed by Phoenix is not a very difficult survival spell generally. It has 4 phases; both the third and fourth are very easy to approach and dodge, so I will concentrate on phase one and two: Phase one, you will want to minimize the amount of dodging you have to do. This is done best by always sticking to a wall. In the video I just linked, you can see that done. I stick to the wall to have as many bullets as possible leave the screen, and I have to dodge much less that I would if I stuck to the middle or something. Phase two has 2 approaches: One is to micro-tap it. Personally, I find that one easier, but most people disagree because they're not good at small, repeated tapping. The other approach is to go in circles and misdirect the arrowheads that was. The phase lasts for a while and you'll have to be careful not to trap yourself circling them. You should try out both strategies and see which you suits you more.
Now, I left out some spells (meaning Forgiving Shrine, xu-fu, HMD), but that's because they're easy. I assume you can capture those after a bit of practice.
The non spells are a bit more threatening I guess, but the harder ones are just random dodging, and you have to get used to that. The last one is very difficult, so just bomb that. 6 and 7 are also tough, so you could bomb those as well.
Overall, IN extra is a fairly easy extra to clear, due to the many lives you get, as well as IN's large death bomb window (which you shouldn't rely on!). the main problem people seem to have is being unprepared for some attacks, as it is very easy to get 4-5 times on Fujiyama if you don't know how to deal with the attack.
