I've been working on a lot of cast iron restoration over the past few days. About a month ago, I took two cracked gate-marked cast iron skillets to a welder and had them sealed. At this moment, the smaller of the two pans is in the oven on its second coating of seasoning; while the larger pan with the wonderfully elaborate handle is in electrolysis right now. With any luck, I'll be able to begin seasoning it tomorrow evening. All of this has put me into a routine, in which I've developed a method that appears to avoid flash rust: when the pan comes out of the lye bath or electrolysis, scrub it thoroughly in the sink with soap, then rinse all of the soap off to leave bare metal. At this point quickly towel dry it, then apply a coating of vegetable oil to the entire surface of the pan, top and bottom, immediately so as to block oxidation. From there, place it on the stovetop burner at low-to-medium heat, in order to thoroughly dry it without burning on the vegetable oil. After twenty to thirty minutes, turn off the burner and let the pan cool off completely. This appears to solve the problem of flash rust: from here, the pan is covered with a layer of oil that prevents rust. I don't consider this to be seasoning, but it lets me leave the pan on the stovetop in this state for a day or more before I get around to properly seasoning it, using Jeff Rogers' method. Over the next couple of days, I give it two coats of vegetable shortening seasoning, then for the third seasoning I melt on beeswax, and season that in the oven at a slightly higher temperature (425 degrees F). And finally, after this comes a fourth layer of seasoning, again with vegetable shortening. I might even do a fifth layer after that, if I feel like it. The entire process takes time, as it's spread out over several evenings of work (since I work at the office during the day).
The gate-marked cast iron pans: www.facebook.com/groups/castironskillet/permalink/549889515094888/