Coffee grinders are the perfect method to add the most surface area to your greenery, though the warm water i disagree with. this is actually counter productive as warm water will wash away the trichomes on the surface of of the pot which is the most pure form of thc available. one of the most rudimentary forms of hashish is made by collecting these trichomes using a screen, silk or otherwise, then gently heating and compressing this 'kif' into a solid form. if your pot butter tastes bad youre either cooking it at too high a temperature or youre using gross pot. if done correctly it should smell and taste like the best thing in the world. if the smell is an issue either to you or the people you live with just cover the pot and keep the temp low.
I agree with everything that OP said, but I find that the real issue with most pot brownies (or any pot food for that matter) is that people are too impatient when making the pot butter (or whatever type of fat you decide to use). this should be a long and slow process, and requires a strict upper temperature limit. the desired cannabinoids begin to vaporize between 160 celcius and 200 celcius, and anything above that begins to destroy (denature) the molecules and made your butter less potent. since we know at what temperature we want this reaction to take place, we can choose the best fat for this application. olive oil has a smoke point of 375 farenheit, roughly 191 celcius, so we would be able to get the lower end of the desired cannabinoid spectrum, but the oil will burn and be unable to absorb anything above 191 degrees. butter has an even lower smoke point, which makes it the most finniky of the available fat solvents. canola (rapeseed) oil on the other hand has a very high smoke point, around 464f/240c, which means it can handle most temperature fluctuations without being ruined. if you want to consider other fat-solvent options, just wiki oil smoke points and pick something at or above 210c. now, the actual cooking part, my favorite method is to use a slow cooker on low for at least 12 hours. 2-4 hours should make some decent oil, but the more patient you are and the longer you let it simmer the better it will be. i like to start it up around dinner time and let it run till noon the next day. when you cook pot this long it turns into a large spongy mass that absorbs a lot of oil so it can be really helpful to have a cheesecloth strainer to help expel and filter the pot oil.
Like COStella I prefer a much... stonier (and healthier) ratio of pot to fat, and also like snarkoleptic its better to use shake and trim. save the nuggets for when you need em, its not like youre gonna smoke trim, so you might as well use it for something.
Also remember that when youre making pot brownies, or anything else for that matter, dont bake or cook them over 375-400f, as this too will damage the oil. Take your time and start out small so you know your limits, everyone has different tolerances.
Peace love and good happiness stuff