1) You need the TXDWorkshop tool or any tool that can open .txd files

2) Open particle.txd with TXDWorkshop (located in your gta san andreas/models folder)

3) Find and replace these textures with the ones in this folder:

coronastar
shad_exp

*This is only if you have another modified particle.txd file and you want to install these textures manually*