Cleaning is very simple and takes less than 5 seconds. Simply take a straight pin and gently push it into the slot above the wheel to force out any grime and grit that has accumulated there. It may take a few pokes to clean it out but when you've made a few passes with the pin you will hopefully be able to see through the slot. If your cutter has a long oil wick you may not be able to see through the entirety of slot but you will see a lot of dirt and debris come out. You'll know you are finished when the pin travels through the slot with very little effort.
Always keep your cutter's wheel in a SMALL amount of oil when not in use. An old coffee mug with a circular piece of sponge lightly soaked in oil is the best place to store your cutter when it is not in use. Just take a sponge and cut it into a circle that fits snuggly in the bottom of the mug. Again, make sure the entire bottom of the mug is covered or your cutting wheel will slip off the sponge and onto the bottom of the mug thus defeating the purpose.