Ashley is a modeler after my own heart. My modeling hero is Shep Paine and my ancient copy of his Dio book is well thumbed and quite beat to hell. Strange, though, I've yet to actually finish a diorama...
Anyhoo, I'll expand a bit on what claymore said. For battle damage, thin the plastic with a dremel or other moto-tool from the inside. Then use a knife to put in some holes using a twisting motion. If there's a bit of plastic sticking out in different directions, that's good. Use references to see what actual battle damage looked like and try to replicate it.
Also, if there is a large enuff hole, there may be some internal structure visible through it. Use any references that you may have in order to find out what might be in there. (structural stuff like ribs and spars, control cables, hydraulic lines and the like) Or, you can use a bit of "gizmology", as Shep puts it. Use a bit of plastic strip, card, some wire or whatever to represent this internal stuff.
If I drop flaps or deflect ailerons, stabs or the rudder , I like to wait until I have the wing together to actually separate the control surface, though it's a good idea to do some work beforehand.
I usually thin the plastic, again, with a moto-tool and cut through the lines representing the ends of the control surface. NOT the hinge line, which runs parallel to the length of the wing or stab but the left and right edges of the flap, aileron etc. (For rudders, if there are any horizontal separations then I cut through these) That way, once all is glued together, all you have to do is a bit of cutting on the hinge line and snap the piece off. Then build up any missing structure with plasticard and/or strip. For a rounded edge, use plastic rod.
Sounds tuff to do, but every unknown is like that. Once you actually do it, it's no longer and unknown. I'd recommend practicing on a scrap wing or something before you try this for the first time on a good model, though.
Fade to Black...