Before applying the sealer, some guys cover the nipple with a paper dot, to allow the nipple to spin for adjustment and not twist up the silicone. http://www.teamincomplete.com/Projects/950/1719tubelesswhee.html
Naphtha (AKA: white gasoline or Colman lantern fuel) is a better choice for cleaning parts before applying adhesive.
We're going to try SM as a better home for this subject, though it could well fit 2-3 categories. Thanks ducatijohn for a great subject.