There're lots of varying opinions on cast iron from what brands are best to how to care for them. I also use nothing else here at the house and most of mine have come from yard or estate sales and antique stores. by far, the two best brands are Wagner and Griswold but unless you find them at a yard sale, you often have to pay fairly high prices for them. Still not always as high as brand new stuff but I don't buy much of anything like that new.
Anyway, about the easiest way I've ever found to clean cast iron is to put it in the oven on a self clean cycle. It comes out a bare dull grey just like it was new. Strips every bit of crud (and seasoning) off of them. I've also done the campfire method on a hot osage fire and it worked real well but the oven is easier.
I have not tried the self clean on a rusty piece, just cruddy ones. I have one pan that was rusted and I tried to sand it clean then season it but the rust has always "shown through" and instead of getting nice and black, the pan has a kinda reddish blotchy look. I always wanted to take it to a garage and have it sand blasted but I might try the self clean first some day. For now, that one sits in the basement....
If you compare the modern stuff to the older stuff you will notice two things. One, the older stuff is not as heavy and two, the quality of the old stuff is much better. By quality, I mean the finish of the inside cooking surfaces. All the old stuff (i.e. WAgner and Griswold) has a milled surface on the inside that is smooth and makes a much better non stick surface. The Lodge, Camp Chef and every other modern brand all come with a basic cast texture both inside and out. Other than the lack of inside finish, the Lodge quality seems very good.
I have a Lodge brand dutch oven that we use a lot for chuck roasts and such but when it was new I took my sander to it and sanded the inside smooth before I seasoned it. Couldn't get the sides as well as I wanted but I did the bottom real good and it helped a lot.
As for cleaning, I generally hit them with a splash of water while good and hot then use a nylon scrubby pad, the kind that look wooly, not the felt looking ones, and scrub it, rinse it and put it back on the heat. The heat will dry it in seconds then I wipe it with a dab of bacon grease or lard and a paper towel, flip the towel to a dry spot and wipe like I'm wiping the oil off. This leaves just a very light film. If a pan has years of season buildup, a little soap won't hurt it a bit but certain foods can damage the seasoning. Tomatos are an example. I guess it's the acid content.
Always be sure to wipe the outside real well too or you end up with a pan that is smooth and slick as snot inside and looks like a burnt booger on the outside.... Then it's time for a burn clean and redo.
As for oil, I prefer lard or bacon grease. I figure it's all that was around back in the days when cast iron was all there was and it worked then, so why not now? Also, it seems to me that some of the vegatable oils don't give the nice hard seasoning finish. Instead, they leave a kinda gummy, sticky residue. I've never had any issue with animal fats and the finish.
One last tip.... If you find a pot or pan at a yard or estate sale, try REAL hard to find out if there is a lid that goes with it. Dang old cast iron stuff didn't have any kind of size standardizaton to it and pots might be 9 3/4" across or 10" or 10 1/8" etc. A good cast iron pot with the lid that CAME with it is like a matched set and fits like a machined part. Finding a replacement lid is pure luck. Thankfully, they usually are together but not always. If you see what looks like a frying pan with a lid, BUY it. Most likely it's what is commonly called a "chicken fryer" pan. They run about 10 to 12 inches across and are about half again to twice as deep as a regular pan. They are about the closest thing to a "do it all" piece of cast iron you will find. You can fry in it of course, but you can DEEP FRY in it too! You can also throw a chuck roast or something similar in there with some onions and taters and use it like a dutch oven. Makes a real good chilli pot/pan too.
Dang, I'm gettin hungry!!!!