they're guidelines for me - no tracing. Usually they don't even have any real features whether they're character or objects or landscape
I look at (say) a scribble that shows two heads talking in 3/4 profile .. I look at other scribble shots of the same characters to see how much else I might need - e.g. do I need whole body or will just the "top half" do? Do I need other views - e.g. full face; side profiles? what actions will they be doing? - and all that guides me as to the character design: I put all the views of each of the characters in a file and then import views as needed into the animation files.
I have often used the tracing system in Anime Studio Pro, I have had very good results unfortunately i wanted a high resolution and but "png" is the best I can get.But I have had good results for tracing to make a characters. Just in case there is a part of the new AS that dose it for you now. I mean get the drawing in one layer and then trace it by hand. I have fount it is much better to have the art in parts. For example the head by its self and fill the screen so you can work to a fine details.