flowing glazes

I use commercial glazes for the most part, and it seems that some of the glazes I buy flow on beautifully, and others seem to "attack" the pot in a thick glob, and dry so quickly that the brush just seems to attach to the pot, and won't glide over the piece. With this type of glaze, I get a very uneven covering. What makes the difference in the two glazes? Is it the components or oxides in the glaze that causes this? I find that Amaco cone 6 is the best I have at the moment for flowing. Any suggestions for other flowing glazes?? I use only cone