Keep in mind that co is for curly hair. If your hair tends to be straight, even for some 2b's, it may weigh down your hair too much.
You may want to look into no heat curling methods. There's several good youtube videos.
Fine hair tends to like protein. Have you tried a protein treatment?
2c/3a-M-ii porous, good elasticity, APL, dark brown with a silver lining. Biggest enemy: frizz!