Pop 1
Despite being the first level, there are some tricky parts, and it's relatively dense with enemies for a single fire section. (The videos here are really bright for some reason, and I'll fix it in the future)

Grab single fire on the first Bobo. The closer you are to the enemy when you start inhaling, the quicker it goes into your mouth. After getting the powerup, there are lots of enemies at different heights before you see Shard 1. The middle clip shows the route most people use, which involves floating up to the top of the screen. My preferred route, on the right, goes in between the two rows of enemies.

The N-Z miniboss is the only enemy that takes three hits to kill. To not get hit by the first normal-sized N-Z that spawns, you can take a step forward before doing the first fire. Another strat involves jumping, the idea being that recovering is faster if you hit the enemy from higher up, at the cost of taking the time to jump. I believe jumping saves a little bit of time, but you risk jumping over the miniboss.

After single firing past several shotzos, there is a Poppy Bros. enemy to combine for fireworks. Throwing the powerup in front of him is the fastest, while going behind him is safer. A nice backup if you take damage on a Bronto Burt is to let the bomb hit you and knock the powerup out of you.

Shard 2 is underneath a bomb block, and since there's water around it, fireworks is useful for minimizing the time spent in it. Note that attacking the Bouncy after getting fireworks is often not necessary if you're at the right part of its jump cycle. The Waddle Dee fight is straightforward. Since the fireworks hitbox lasts for awhile, it's easy to anticipate when Waddle Dee becomes vulnerable. After four hits, throw the powerup for two damage for the kill. Float up after grabbing Shard 3 so that Ribbon goes back into Kirby faster and the fadeout gets triggered sooner.