One way with the coffee cup is to go to the store and pick up a package of Dill brand pipe cleaners.
Coil up the pipe cleaner leaving a section about 1-inch log straight.
Punch a small hole in the bottom of the coffee cup with a pencil or pen and insert the straight section of the pipe cleaner through the hole on the inside of the cup and bend it on the bottom to hold the coil in place in the bottom of the cup.
Drop 4-6 drops of super glue on the pipe cleaner coil and place the cup over the door knob and secure with a small strip of tape. The fuming process should only take about 5 minutes.
You can also place the cup over small items for fuming.