It darkens things a little, especially if the vibrator is left running overnight or for several hours. A couple of fills with the almost-boiling degreaser and 2-3 hours' running time each is a pretty good time frame. After softening the deposits with the TSP, I do a boiling water rinse and an immediate air cleaning. An instructor at the old GM training center in Memphis used to tell us "Put 55 gallons of air through every passage!" I use a needle-tipped blow gun and 100+ PSI of air pressure for that process.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!