The key to getting a really good seasoning is to never, ever let soap touch the pan. That also means the fry pan can only be used for frying greasy stuff, and not boiling anything. I wash mine under warm water using a
plastic scraper, and then wipe on a layer of oil to store it. After a few times around it's nearly as nonstick as teflon including fried eggs with no sticking. The dutch oven will be for pot roasts and chile and whatnot, so don't even try to season it.
If you shop at garage sales, take along a ruler. If the pan has ever been way overheated and then quenched it may have a curved bottom that will never sit right on the stove. Besides being tippy, the limited contact area tends to make for slow heating with hot spots on an electric range. Also a pan like that is going to have thousands of pounds per square inch of stress frozen in, so it could possibly shatter like glass if you smack it a good one or overheat the piss out of it again. Not likely, but I'd pass on a warped pan anyway.