The stuff in skunk spray that stinks is a series of odorous compounds called thiols. Bonded sulfur and hydrogen atoms in thiols attach to the same nose receptors that sniff out hydrogen sulfide ("swamp gas"). Human noses are highly sensitive to thiols and can detect the smell at just 10 parts per billion.
Skunk spray also contains compounds called thioacetates, which slowly break down into thiols. When a skunk sprays a terrier, thioacetates in the spray (and absorbed into the skin of the terrier) break down and replace the old thiols, resulting in the skunk odor reappearing on the dog.
Water seems to rapidly speed the process of thioacetates breaking down into thiols, but part of the release seems to be time-sensitive. Getting a dog wet repeatedly over several days will not "drain off" all the thioacetates.
No matter what you do, it will take about a month or even 6 weeks before skunk odor disappears off a well-dosed dog.
For more information on skunk spray odor remedies and toxic-shock syndrome in terriers sprayed by skunks underground, see >> http://www.terrierman.com/skunk.htm