One note about spirit gum, from personal experience. Make sure to clean the skin oils off well. Do not use moisturizing soap (which is what a lot of hotels supply). You may want to use astringent/toner.
A couple of years ago, my husband cosplayed as Zelgadis (3 hour makeup job!!!) We had, of course, practised all the application at home. (So you know how it will look, how long it will take, how much of a pain it will be to get off, and whether you have nasty reactions to any of the makeup.) At home, it worked well.
At the con, however, his ears were falling off within a 1/2 hour. In fact, all of his latex was peeling up. We couldn't understand why... until somebody asked about the soap. Ivory at home, some moisturizing stuff at the hotel. There's a bar of Ivory in the makeup kit now...
Member, Not Ready for Bandai Players
*Website coming soon!*