You shouldn't find any of these things in children's paints but they are often found in professional artist's pigments. Here is a novel idea that really works and saves on scenting oils. After the soap has cured, saturate a bit of muslin in the appropriate scent and layer the soap bars with it. Store in a tight keeper for about 3 weeks. The scent seems to penetrate clear to the center.
Shrink wrap is very good at holding scent in the soap.
Unlike plastic which breaths, cellophane is impervious to essential oils and won't let them pass. Use this to wrap your finished soaps and they won't lose their scent. Using DPG, the soap often cures in 24 hours and I have used it that green quite often. I cure the soap in the tubes until it is waxy and hard. To remove the soap I warm the tubes in a Coleman cooler.