1. Is is ok to clean plastic drag/handle knobs in Dawn dish soap/water?
2. Is White vinegar & baking soda ok?
3. Spools with drag washers removed?
stick with plain hand dishwashing soap and water. i used machine dishwasher detergent that contains sodium carbonate one time. it's mildly corrosive, but it ate through the anodizing of a nice reel. my mistake.
Alan is right. Just use HD Dawn with warm water for plastics.
I use this with a small jar/vat mixed with warm water for just 5 minutes in the Ultrasonic Cleaner for handle knobs, drag knobs, any other plastics, and plastic spools.
After drying completely, I apply some WRL191S synthetic oil, allow the parts to set for 5 minutes while doing the rest of the reel —- then wipe off the oil completely from the plastic parts with a quality microfiber cloth. No muss, no fuss, easy and safe. Turns out and buffs out like new with no issues or effort.
Best, Fred