I did the same thing on an old winchester 67 22, using Casey's stuff, and had the same problem my first time. I did it over the winter, in the garage when it was cold and that was the first problem. My secondis I treid to modify over their instructions <thinking I had some common sense>.

Get all the old blue OFF, all grease OFF, Wash the metal and never nver let your skin touch the metal, use latex gloves from that point on. Get the metal smooth and shiny, getting all the grit off after using your emery paper. The better the surface, the better it takes. Then do the actual blueing in a warm area, ventilated.

Take the time, it really can be a great finish.