With welded wings I use a grinder to cut most of the wing off, then attack the remaining welded flange section ie top lip, vertical door shut etc (its easier to work with narrow sections of wing) sand/wire brush paint to find spot welds, use drills then thin bolster chisels and clean up with sanding disc on a grinder.
ps remember to use zinc rich primer between the existing and new metal....its know that Viva wings need to be replaced more than once following restorations.