Rust bluing is a good alternative to caustic tank blue, but not quite the quick and easy process some folks think it is. Doing rust bluing properly requires good preparation; some equipment, including a tank large enough for the gun; and a whole lot of time and patience. Its advantage over caustic blue is that it does not require caustic chemicals with the accompanying danger.
In reading a number of threads on bluing, it seems that what some people are calling rust bluing is nothing more than cold bluing applied to heated metal. That type of bluing is only marginally better than the normal cold blue process and will not do a good or lasting job.
But there is an alternative in the form of one of the paints available today. Some of those are durable, relatively easy to apply, and, if they don't look like a good bluing job, will at least cover up a bad or damaged finish. And paints have the advantage of requiring little in the way of equipment