use layers..i think its complicated and also i've noticed that if you enable autosave and exceed a certain number of frames in your drawing process,say 1,500,then there might be an error and everything comes to a standstill ,i always have to restart the comp and it can be frustrating..does it happen to you ?

great drawing...Hats off if its original,even otherwise hats off because it's drawn very carefully and i can see that you worked hard ..these manga people have huge eyes and innocent expression..Although i'm not personally a fan of manga..their looks can be disarming .. way to go