Below will show you what the whole process looks like in video form:
Find a dark place or room to store the seeds. In order to germinate the seed needs to be in darkness so avoid places where light could leak in.
Bringing Down the pH
Sure, you can grow autoflowering plants using rock wool cubes outside or inside. If you are using the large cubes you can put them into a fabric container, plastic, etc., but they do need a place for the water to run out of them when it rains and when you water.
Now I had to mix a proper pH water solution to soak the cubes in. I filled a plastic food container with Brita filtered water (don’t think this is needed, but why not?) and added 0.25ml (a few drops) of pH Down. I stopped when I got to a pH level of 6.1.
Wait for Sprouting
From this Question & Answer post someone asked if you could use rockwool outside and answered:
The FloraFlex 6-site kit is a rockwool hydroponics system that automates watering for six 6″ x 6″ rockwool cubes.
If you need to buy the humidity dome and also need a heat mat, check out the Soligt tray with humidity dome and heat mat.
HID lighting: Metal Halide or High Pressure Sodium
If you check out Amazon you’ll find a bunch of options. Here are a few to consider:
The HighFree 6 site hydro system is an entry-level rockwool hydroponics kit for starting small cannabis plants.
Can rockwool be reused?
Heat mats speed up germination for cannabis seeds in rockwool. They’re generally inexpensive and are a worthwhile investment regardless of whether you’re growing in rockwool, soil, coco coir, or any other medium.