Cannabutter is not like making hash or oil you don't have to screen it, but I do prefer to dry it first.
I usually take my dry trim and let it soak in some water for a few hours, this removes a lot of the foul tasting elements as things like Chlorophyll are water soluable while THC and other cannabinoids are not.
I then heat the water just until I can melt some butter or margerine, and let that simmer for a while. I next remove and strain the marijuana, and rinse it to make sure that all of the butter or oil is removed from the spent marijuana.
Then just throw that in the fridge overnight and the butter will float to the top and harden on top. Then just remove the butter floating on top and place it in a container for storage, I like to use old margerine containers.
Then you have cannabutter that can be used in whatever you desire, even eatten off of some toast.
But this is just what i do