I do not have a teacher but I have a monk who agreed to help me through my Buddhist path. I've told him I practice impermanence and metta, I told him a little bit how I practice impermanence and he had nothing to say but I think he didn't understand me because he said "when you sit on impermanence" but I basically don't sit on impermanence I do it everyday in this type of way "the rain is falling but it is impermanent it won't last forever, I am feeling anger this is impermanent, I feel happy this impermanent" and I go like that through the day. I do sit for metta though. I wanted to practice on death next because of my ptsd and bipolar the monk told me I can't do samatha and vipassana, it brings back memories that aren't healed yet.