Get yourself a strainer, like you use to strain noodles. Dump the hydroton in the strainer a flush it out with water. Then do it again. That stuff has a lot of dust on it, and must be cleaned.
Rockwool (since its made from stone fibers) has a higher Ph than is prefered in Hydroponic growing. Therfore a overnight soak in 5.5 or lower Ph solution(as low as 5.2) is the norm. Since I have a Top Feed DWC I dont do that. I just put them in and my recirculating pump does the work. WOOT WOOT!!!! Soaking the hydroton in lower Ph water after rinsing is the norm as well but preferences differ. I rinse mine out with tap and add to pot(again because I have a Top Feed DWC)
I rinse my balls but still everything gets coated in red. if I didn't rinse them I would worry about damaging my pump, there's so much dust
the best thing to do with new hydroton is take your shower head off, stuff the hose in the top of the bag, knife the bottom of the bag and just let the shower rinse your ball bag out