When I started out on my own and left the fold of the classroom/co-op about 2 years ago I had a few rules that I was going to stick with. They were just what I set out to do and one of them was never to use a pre-mixed glaze. I wanted the experience of testing and learning. It was good time spent with some successes and yes some failures, but in the end I have a set of glazes that are my own and I can repeat them easily whenever I want. Again I am not knocking the pre-mixed glazes, it was just my choice and how I decided I would take my studio journey.
I have two small shelves of material (IKEA shelves), and a small 4'X2' table that I have my mixing. I use 6 gallon buckets for mixing and I store them in 10 gallon covered tubs. I use a triple beam balance for all weights, even small tests, and I sieve twice, one at 60 and one at 80. I have a glaze slop bucket that all tests go into and when I need an iron saturate glaze I use it (it is a pretty nice medium dark iron rich glaze that fits perfectly). I test my slop with a test tile at every firing so I know how it is changing.
Sure I made a few mistakes in my initial ordering because I did not know the material, like buying 10lbs of chrome oxide.... it will last three lifetimes. Such is life.