For my cast iron skillets (now in several sizes!), I always do the same thing. Cook with them as normal. Clean in the sink with Dawn (grease cutting genius), a sponge, and/or my fingernails as necessary to remove stuck-on junk or fat. Then I put the wet-but-clean pan back on the fire and blast it until dry. (Leaving water in a cast-iron pan is a great way to get rust.)

This seems more than sufficient to maintain the seasoning. If I feel the seasoning is lacking, I'll cook up some bacon. That pretty much solves that problem. For brand-new cast-iron cookware that isn't seasoned from the factory, you can brush on a thin layer of bacon grease and put in the oven at nuclear-hot for a few hours. That's a start, but really it's the continuous cooking, over and over, that really does the job. A good seasoning isn't necessarily all that thick. It's just uniformly dark.

As to charred food stuck to the pan, that just means you needed to add a small amount of cooking oil to lube the pan before putting in whatever you wanted to cook. It's important to keep in mind that a well-seasoned pan isn't at all a no-stick pan. It's just a bit less sticky and a bit less likely to corrode.