The simplest test would be to use the liner glaze inside and out on one pot and the outside glazes on both inside and out on another pot.
In addition you can test the relative coe of the clay by using a series of glazes with varying coes. Studio potter had an article on this topic. I think it was by Jim Robinson.
edit: Here it is.
These should work for you.
This same technique is outlined in Mastering Cone Six Glazes as well.