How to use sprayable toxic gas?

How to use sprayable toxic gas? It says it needs a chemical thrower. But I can’t find or make a chemical thrower. I am trying to fight triffids.

This is what you want. Here is the ammo. This is the magazine the thrower will need to use.

Crafting the chemical thrower requires the launcher skill.
But there is no crafting recipes to train that skill:

Other then practicing with a launcher you find yourself, you could read a few books: This magazine may be easy to find. Also: All ranged skill books.

You can train launchers with a spraycan flamethrower, incidentally. Combined with a beartrap it makes a decent way to kill juggernauts.