You cannot mix the sulfite in glycol. Substitute some ascorbic acid. I forget how much, but it's not much. The sulfite in Pyrocat activates the superadditivity between catechol and p-aminophenol. A small amount of ascorbic acid will serve as well.
You have not seen the latest about heating glycol. If you use a Pyrex saucepan and cover it with Glad or other brand of microwave-safe plastic wrap, and leave enough slack so that the wrap rests on the surface of the glycol, you can see the instant boiling begins and remove the saucepan from the stove. That temperature is very much higher than you will need. No vapor can arise from the surface without lifting the plastic, and none can overflow the container without breaking the seal between plastic wrap and container. If you heat the glycol container in a water bath, or use a double boiler, you will not be able to boil the glycol until the water boils away, if then. The only purpose of the heating is to speed up the dissolving by reducing the viscosity and increasing the molecular motion. If you have a stirring device, magnetic or other, and can wait long enough, lukewarm will do.
