Waterpik is a great idea! I cannot believe the number of times dental stuff has made its way into keyboard conversations LOL.
I was using a kitchen sink sprayer somewhat successfully but water would go everywhere and still required brushing.
I gave in and ordered an ultrasonic cleaner from Amazon that ManOfInterests mentioned in, Prime Day Deals for Keyboard Peoples - #3 by Manofinterests. It is tracking at a decent price of $47, https://camelcamelcamel.com/. Should be coming in tomorrow. I will report back on how it works on the diamond paste residue.
Also will need to find some other uses to justify having it. Maybe using it on eye glasses or something so I don’t feel like I am “wasting” money. If anyone has anything ideas let me know.