I know about those handles, I have one. When my husband or I wash the processor
it is impossible to get that thing dry. I leave it out on the counter until I see that it is totally dry before putting it into the appliance garage. I would make a solution of bleach water, put it into a large bowl, then place that handle so it is submerged in water. After the job is done rinse well, dry as best as you can, then take your hair dryer to finish the job. If you have a spare hair dryer it may pay to keep it in a kitchen drawer just for that job, especially if where you live is humid.