I don't know if this will work for all of you fine, thin haired curlies but... I found a new trick. I'm not sure if it's product and the trick or just the trick. What I do is wash and condition, rinse and lightly towel dry with a microfiber towel (I've always done that part) but then I'm using a small amount of ouidad playcurl mousse and I scrunch it in but then I run my fingers up into my scalp and shake with fingers. I do this on both sides and then in back. I've done this with dry hair and it didn't do much but on wet hair - it seems to give it volume. Then I add whatever gel I'm using and scrunch that in and then diffuse. GREAT volume and good curl formation to boot.
I've tried everything else and nothing else has worked. So, give it a try and see if it works. I would be curious to see if it works for others too.