You need to apply glue first to one sheet, then let it dry. When joining the two pieces is when the iron is applied. I tried this with several airplanes on D-tube wings going back to my R/C sailplane days. Once you get to the point where you are ready to apply the leading edge sheeting, you apply glue,( usually aliphatic resin or carpenters wood glue,) to the ribs, spar and leading edge, and let it dry. Set the sheeting in place along the spar making sure it's even, then tack it in a couple of places with the hot iron. I think I just used a monokote iron. then run the iron along the spar slowly to set it in place. Then start with wrapping the sheeting along the ribs down to the leading edge. This part goes a bit easier if you preshape the wood a bit first. When you get to the leading edge, finish that off. Then sand as required. I never had a problem with a wing done this way. BUT!!! It only works on the first try. If something doesn't go correctly, you have some work to do to fix it. I don't know how it would work on a large area sheet lamination, as far as warping goes.
Type at you later,
Dan McEntee