Boil your cannabis with the butter and water. Put it in the refrigerator for 24 hours and pull out the butter, wash it off and blot with a paper towel, being careful not to let it slip. Wash your pot again and put the butter in some fresh water and boil it again, then pull your butter out after it is in the refrigerator for a day or so. Your butter should be a golden yellow color (unless you use ABV, I have not infused any butter with that personally). I do not like the taste myself at all. If it is yellow right off the bat you should be good to go.
You could also do a quick wash with ethanol and infuse butter with that, too.
You can even make nearly tasteless stuff from fans as well with some patience. The stinky smelly stuff will go into the water, and the good stuff goes in the butter. Use coconut butter or real butter. If you are just tossing in some trim into a recipe it will taste like decarbed cannabis and may even upset your stomach. It does mine.
I have also went through the steps, and added more fans to up the concentration of cannabinoids per gram of butter, then do washes until the taste is better. Not even the source could pick out which was fans and which was sugary trim.
Skunkpharm has a time vs temperature graph if you don't turn it into extract first but if you do turn it into extract first you can follow the same timeline with a hotplate or oil bath of some kind. Just watch the bubbles in the extract if you go that route.
Oh, as far as concentration, butter should be able to hold around 15 mg/gram of butter. I figure for trim it is 6-10%, fan 3-5%. I would never use buds to make butter, unless I was rolling in them. I would do a QWET extraction and let it naturally decarb in a case like that.