I did some glaze testing last weekend.  If one of my students took the approach I have I would tell them they were doing it all wrong.  On the basis of one test that was over-fired I've chosen a glaze.  I needed to place an order for materials ASAP in order to be able to finish my project by the end of the summer, and of course I wanted to order all of the material together to save on shipping, so I had to decide on a glaze right away.  I wanted a base that was satin and would not obscure decoration underneath or cause oxides to run.  Of the four tests I did only one really fit the criteria.  Of coarse it was over-fired so I'm gambling that I will continue to like the results, but I figure if the glaze looks good over-fired it can't go wrong.  I'll do a better job of testing when it comes to adding color.  The base I ended up choosing was one of the high calcium semi matte glaze bases from Mastering Cone Six Glazes.