Or you could just build small/medium fires for a week and dry it out. The whole "curing" thing is overrated. Especially if you use blankets/board for insulation instead of perlite or vermiculite, there isn't that much water in it to begin with, and refractory cements do not cure the same as portland/lime ones do. They do not want/require a 28 day cure like concrete, they reach strength much faster and are less prone to shrinkage, which is the cause of most cracking. If you are curing a castable, you should let it dry at room temps for a week or two, then fire it as high as you want, but doing so gradually. That is the key to curing, gradual application of heat, gradual being hours not days.