Really! I've already tried out the tutorial below, as I had gone to the craft store to purchase some today. I needed a few colours, and my local store only had two packs of colours for almost $20! I would have needed to spend almost $80 to get the colours I wanted...I just couldn't/wouldn't do it. I happened to have all of the needed supplies on hand including spray bottles that I had purchased to make perfume in. I also happen to have a crazy supply of mica for use with mineral makeup - so I really was all set.
I'm off to make more - mixing the colours is quite fun :-)
A couple of notes
1) The bottles I had fill 60ml of liquid. I filled it up a little more than half way with water - then just poured in the mod podge. I wasn't overly careful abut making it half/half. The more water you use, the less likely your spray nozzle will clog up.
2) I used a lot more Mica than she mentions in the tutorial. I started with three heaping knife edges worth - mixed, then tested the colour on white paper. Keep adding more until you are happy with the colour.