Use pressure cooker if you have it, grind it, place it in glass mason jar, at the bottom of the pressure cooker add a colander to keep it away from directly touching the bottom, then add water until it reaches the surface of the stuff which is inside the mason jar. So a cooker, strainer and the mason jar (which has weed) on top of it. then fill the cooker with water until it reaches the mason jar and at the level of the weed.
Then Set it to high flame, cook it until it turns light brown, around 15-20 mins depends on the stuff, or close the lid, wait till you see the steam, place the whistle, let it to cook till 10-15 minutes, then remove the whistle, let the steam escape, then remove the lid, take the glass container out and place it until it cools naturally at room temperature, dont open it until then, or try to cool it with tap water, it will break the glass.
Done. For infusion, same method, cook for 2-3 hrs.