After you decant a fragrance with a mini funnel, how do you clean it before your next decant? After you decant a fragrance like Black Afgano, you really have to clean it out good before decanting your next fragrance.....
Agree with the others. Plastic funnels or pipettes are so cheap that there's no need to reuse for different perfumes.
That said, repeated washing and air drying (over the course of days) should avoid contamination. Whatever remains on the funnel will be overwhelmed by the new perfume.