What most people do is grind many mushroom up together in a coffee grinder. This results in a power with a uniform average potency. Just be careful not to accidentally spill it or inhale it. If you live somewhere where it is legal, you might be able to work something out with an organic chemist at you local university and get a pure extract. Psilocybin is so safe that there’s really no harm in taking .2g instead of .1g the main challenge is cycling it so you don’t developed a metabolic tolerance. Pretty much the opposite of an opiate situation.