IT'S RANK MANAGEMENT BRO!!!!!!!!1!!!!1!!
I heard that if you collect only the small medals and every powerup you see it makes the game easier, I heard it from a pro shmup player.........
It's less about rank management that early in the game, more about just getting more bombs so you can get 2 million free points and extend back up at the flamingos.
A very fun way to play is to never suicide, but have 1 seeking option do all the dirty work. Works best with Miyamoto.
I'm nowhere near the really good shmup players, but I've 1cc'd a handful of shmups including Garegga. I suck at other games. I straight up broke a controller in rage while playing Dark Souls.
Which character do you use? The easiest clear is going to be with Golden Bat (wild snail ABC type), probably followed by Miyamoto (C type).
Stage 6 is a pain, I almost always use a bomb at the turret wall, and directly after it you will want to get seeking options (drop exactly 5 bomb shards, then get next option).
Let me know if you have any questions about it.