First off you can't "scrape" the seasoning off of a cast iron pan. The oil or fat that is used to season it is used so that it soaks into the pores of the pan and seals the iron. Using salt and/or soap can remove that seasoning because they both will remove oil substances. The more you cook with your pan the better it will get. If food is stuck on the pan after cooking, simply soak it in very hot water til dinner is over and the food will fall right off, just as GotGarlic suggests. Letting it sit and cool with food particles will cause them to stick. But the more you use your pan, the less it will cause food to stick.
After washing my pans with a stiff brush and very hot water, I simple dry thoroughly, put them on the burner with a thin coating of Crisco only on the inside, then leave on the burner on high for about 60 seconds. Off the heat and let it cool on the burner. It's a constant seasoning process without having to go through the whole oven thing. I use my cast iron in the oven often - even roasting chickens in the pan makes for a beautiful crisp, mahogony colored bird and at the same time it does wonders for the pan. All of my cookeware is cast iron and the black Lodge pots and pans are a gorgeous, smooth black from the constant use and no soap ever. The splotchy look will go away once the pan gets more use.