Particles

Select the icing, find the Particle panel.

• Click + to get a new particle set, and change it to Hair.
• Under Render, change Render As from Path to Object and pick the object. Boom.
• Scale up/down to get the size you kind of want.
• Scale Randomness isn't great for sprinkles since you want uniform thicknesses.
• Under the "Hair" indictor hit Advanced so we can do something about the direction.
• Rotation, check the box, change Orientation Axis to Normal.
• Not (much) Randomize 'cause that'll make them stand up, but Randomize Phase instead.
• Emission -> Number, obviously that's how many dingdang sprinkles we want.
• Sprinkles showing up underneath the icing? Weird! Time for Weight Painting!

When you've done Weight Painting make sure to select Density = Group to apply what you've done.

Firework:

• Start with your basic isosphere as particle emitter.
  • All particles all the time at this point.
• We don't want constant emission of particles so we set the Emission -> Frame Start/End to 1 (maybe play with the end frame a BIT?)
  • Lifetime should be longer, hundreds or possibly thousands of frames.
  • Number is obviously going to be important.
• Field Weights -> Gravity should be turned way, way down. Probably in the .1 to .3 range, as low as looks good.
• Physics -> Physics Type to Fluid instead of the default Newtonian to get more flowing/wobbly effect.
  • While in Physics, crank up the Mass. It paradoxically makes the particles themselves smaller the heavier you make them...?
  • Toggle Multiply Mass With Size too.
  • Physics -> Forces has three values to possibly fiddle around with.
    • Brownian motion is nice, only need a few integers' worth though.
    • Drag does some interesting things with slowing down the particles after the initial burst
• Velocity -> Normal goes up a bit, maybe 3-ish? Make note of the Randomize option, it spreads the groups of particles out a bit.
• Emission -> Source -> Emit From, change from Faces to Volume so things aren't clumping up based on the faces
  • Tutorial dude hasn't seemed to consider just making a higher-face-count sphere? May want to toy with that for reasons?
• Making our custom particles
  • Go to Render and switch Render As to Object and turn off Show Emitter.
  • Make a new icosphere, turn Subdivisions down to 1, this is our super low-poly "particle" source object.
  • New icosphere, add material. (We can dupe these if we want more colors, but for our immediate purposes we don't care.)
  • Surface should be Emission instead of Principled. (Is THAT how we make lights from objects?)
  • Go to our original icosphere and under Render -> Object we pick the new shiny icosphere as our Instance Object
• Scene can have Bloom on, I guess that's a thing we may want? Also blacken the world at some point.