this vid shows how they make firework shells in japan and yes normally the chinese are doing that

at the first part you can see how they make (and dry) the 'stars' what create the actual effects of the shell

the second powder is blackpowder with rice hulls that will create the explosion in the
air and separate the stars across the air

the last part of the vid shows how the shells are paste in, dry and get their fuse
(partially)

(if the music is annoying to you please mute it)