some people think of 'rinse & repeat' as doing the 1st step a second time with the same interval of sitting on the scalp... not a good idea.
what ya can do, is first put about half of what you normally use in a standard nizoral washing session, into your hands.. do a lather with that for about 30 seconds.. rinse it.. THEN put the second half (of what you would normally use in a standard session), into your hands and lather again, this time letting it sit for the good 3 - 5 minutes.
That way you don't over-due anything... and you get a good pre-cleanse which helps the second one get through your skin better.