It's no picnic if you are as picky as me. Heat helps but the glue is in the color and much of the color will stay behind. It can be cleaned with Trim Solvent or the like but is a mess. It's not a big problem unless you are going to put a light color where a dark color used to be. If you are using the same colors just get it smooth as possible and leave the rest.
The other thing I would ask, are going to cut the hinges off and recover the surfaces or are you going to cover on the plane? If you are going to leave them on than I would leave some of the covering. Leave all the areas of bevel and the inside of the surfaces like the area between the start of the AILE close to the wing. Then when you recover just overlap as close to the centerline as you can so it wont show.

David