Why did rust appear after my first layer of seasoning? I have a brand new, unseasoned, cast iron dutch oven and an older cast iron skillet. I wanted to prep both for some upcoming camping trips. I found online that flaxseed oil seemed to be the best option for seasoning a new or old pan so I tried the method suggested (start with unseasoned pan, bake at 200 degrees to open pores, apply thin layer of flaxseed oil, bake for 1 hour at highest temperature available on oven). 
After just 1 layer of flaxseed oil to my brand new dutch oven, instead of getting a slightly darker pot I now have a pot completely covered in rust!!! Where did I go wrong?
I've tried using steel wool to scrub away at the rust but I'm not really getting anywhere with it.
what do I do now? Do I try a vinegar bath or oven self cleaning cycle? do i try to season over the rust?
Even my older pan developed a reddish hue in some areas! (i'll admit i did leave some of the old seasoning on because I was too lazy to completely strip it)

Help! I'm newer to the world of cast iron and I'm not doing too well :(
Are you sure it is rust and not oil residue? Is it sticky?

In your case, I would try to clean the pan by heating it on the stove with some water in it. Use low to medium heat. Once it's warm, use some balled up tinfoil to agitate the surface of the pan. If it's really caked on, drain the water and try repeating the process with some beer or liquor as a solvent..that will usually do the trick. Wipe down with damp or dry paper towels to remove residue. Repeat steps until clean.

Once clean, I typically air dry or heat the pan back up on the stove on low heat to get rid of any residual moisture. While it is still warm, lightly soak a paper towel with vegetable oil and wipe the whole pan down so that it is lightly coated in oil. This will prep it to be cured in the oven (so the oil doesn't spoil)

To cure it, I usually don't set the oven too hot. 350 degrees Fahrenheit or so for 30 minutes is usually good enough for me. The point is to get it hot enough to cook the oil but not to burn it. Afterwards, I will wipe it down lightly with a dry paper towel if there is any excessive amount of oil and just let it cool in the oven with the heat turned off. The pan should be somewhat shiny in the end.

Hope that helps.