I’ve found that using a method that works for classic muscle car steering wheels, headlight switches, etc. also works for the Becker knobs.
Toss ‘em in the dishwasher. There is a property in most dishwater detergents that gets rid of the sticky surface. If you don’t have a load ready to run and a captive silverware device (small plastic cage for plastic lids, etc.) then you can simply put a few drops of liquid dishwasher detergent (I recently used Cascade) and rub the knobs until you get a black slurry going, rinse and repeat as necessary. Generally, I’ll do it once and set the knobs