Hiya – I’ve had success making swirls that don’t blend, by waiting until the last possible minute to add the colorant/dye. Say, for example, the Pot Time (time your resin/catalyst takes before it becomes too hard to add anything else) is 7 minutes. At the 6 minute mark, I would drop in the colorant. (I actually used a toothpick with some black dye, poked it straight in and pulled it out slowly while giving it a gentle swirl or corkscrew motion). If you want a second color, do the same thing, but keep in mind the Pot Time.
Hope Katherine doesn’t get upset that I answered your question. 🙂