SunRise, another way to get straight lines is to use a fragrance that accelerates. Split your batter as earlene suggests but don't add the FO. Whisk the FO into each portion just before pouring, and it should set up fairly quickly - at least enough to support the next layer. If you are attempting LOTS of layers, Toni of White Milk Soap keeps her lye solution, fragrance and oils separate, then weighs out mini batches. I've done this, and it works well - but be prepared to spend a very long time making your soap. It also helps to have a gram scale. Here are a couple of YouTube videos she made using this technique.
