I had good luck with just FO & color. I have used the liquid candle dye and the soap dye and like the soap dye better. Seems to dry faster. The only time I had an issue with greasy looking salt is when I added too much FO. I did put it on once, let it dry and reapplied more FO for a stronger scent. Seemed to work ok, I put them on a cookie sheet lined with foil and sat it under my halogen lights under my cabinets. I'm not sure about the glycerin, maybe that is to add sheen to the salt but I don't feel it is necessary, unless I am missing out on something. I hope that helps you a little, I'm by no means an expert but this is what worked for me. Good luck, I hope you find the answer you are looking for.