I had a complicated scheme for prewetting ready to post but couldn't see the value of it. If you do prewet, I would suggest using a small amount of nonionic wetting agent in the prewash. Something like propylene glycol, maybe. It may be that keeping Phenidone or p-aminophenol base in glycol to mix with the ascorbic acid-borax solution will preclude the necessity of prewashing.