I used Sig Core Bond, it worked great. Recently I tried the Dave Brown Sorghum with slightly less results. I have heard that people use gorilla Glue, (plyurethane glue). They swear it works great. I haven't tried it yet.

I use Monokote. Just feep the iron moving. If you hold a piece of 1/16 in your hand and touch a hot iron to the other side, you will realize that the balsa has remarkable insulating characteristics. But you can still feel some heat if you hold it there to long.