Burn them in the fire, still going high...it will not hurt the iron. Let the 'crud' burn off. Once they have cooled...I'm talking cooled off.
Season them with lard, or shortening...cover them completely. This time set them on a rack above your campfire....it smokes the house up too much to do indoors...let them get good and hot that way...again...let them cool...then you will have cleaned an seasoned skillets. This may have already been stated.
Keep them seasoned after you use them, do not use soap if you can help it. I do use water, though some say never. I simply recoat them once I have washed and dryed them. To dry them after washing I place on the stove and reheat till all water is out, grease lightly & hang or store till needed again.