don't know that it matter much if the boxes will be in a place where they won't be tossed around. cold wax is very brittle. hot wax with no bees on it, sags. i wouldn't do more than you know you can use before the weather is hot.
with the wedge tops, i like to glue them in with a bead of wax. there are devices made for doing this, but i got an old glass syringe off ebay that does the trick. it seems fussy, but it doesn't take long with a little practice. i melt the bees wax in a soup can in a pan of water. it doesn't take much.