How do I mix bulk Bath salts?

I'm looking for a machine for mixing bath salts with coloring and essential oils. This is not for a small home made batch but for bulk batches of 100lbs at a time. I've heard they are mixed in drums or some sort of industrial mixers but would like to find out the exact machine (and if possible process) for doing this. Thanks in advance!How do I mix bulk Bath salts?
Worked at an aromatherapy company. Only saw it from a distance and never mixed the stuff myself, but it was definitely a small cement mixer.





One example from eBay:


http://cgi.ebay.com/5-CU-FT-1-2-HP-Porta鈥?/a>


or just go to eBay and search ';cement mixer';