We're busy sanding back the paint on our Rimu stair stringers (I think that's what they are called - the bit that goes up on either side of the stairs and holds the actual steps) so that we can varnish them to make a feature of them but we have some areas where the previous owner has put white gap filler in to spaces between the stringer and the wall and we're have a hard time getting this out to replace with wood putty. Does anyone have any advice/recommendations on a good way to remove the gap filler?