Are you referring to the tan rough stuff that builds up over time at the krausen area?
I really don't use anything other than Oxyclean, warm water, fingers and occasionally a blue scruby on the back side of the sponge.... I have used my buckets for 2 years with no issue and I have no worries / concerns going forward.
I brew the best beer around.... don't believe me, ship me a keg of your finest and I'll email a picture of me testing your beer with a write up....
OnTap: Rocky's IPA
OnTap: Wife's Ale
Fermenter: Vanilla Porter, Riley's Smile, Mead
OnDeck: Wifes Ale, J da Arrogant Bastard, Js Pale Ale, Rocky's Bark