To utilize leftover marijuana components - sticks, water leaves and the like - simply put it in a double boiler with some butter, and let it simmer on low heat for 24 hours, then strain out the butter and put it into a plastic container in the fridge.
It's easy to make several cubes (equal to a stick or 4 ounces) worth of pot butter in this fashion ... and half a cube is about the amount of margarine or butter one uses when one is making brownies.
No vegetable material actually enters the mix, such that the resulting brownies are substantially safer to carry.
I've spent maybe ten years playing with petroleum ether and sundry other solvents, and for me it's really a waste of time trying to make hash with small amounts of marijuana.
The cost/effect ratio just isn't justifiable. Whereas the same materials, when invested in pot butter, not only utilize every component, but can get a whole room full of people high ... or keep you sane for a few weeks.
A double boiler is simply a large pot with water in it, which contains a smaller pot with the marijuana and butter in it. The water in the large pot boils, heating the smaller pot but never exceeding the temperature of the boiling point of water.
Always use a double boiler when working with any kind of material that may combust if it comes into contact with a flame or other ignition source.