You can add shellac to the finish at anytime by dipping finger in shellac the with a few drops of oil instead of alcohol if you think it is to thin in spots. The idea here is to smooth the rough brown looking shellac so the clear coat is smooth and shiny. Then we usually add more shellac finish if needed. The alcohol is actually melting the old shellac so it will blend with the shellac that is smooth. We are not removing shellac just redistributing it.