You might need two crates, one for each Lab.
Mainly you feed them for being inside the crate. Give them all their treats and toys - inside the crate.
Then gradually up the challenge by shutting the door for short periods of time then longer periods of time. If dog barks or gets too excited - you might need to cover the crate up with a sheet. If the dog starts pulling the sheet into the crate - you need to put a card board moving box or two flat over the top and then the sheet - so the sheet does not touch the sides where the dog can reach it.
If the dog is quiet, you lift up some of the sheet...
But ideally you've opened the door and fed some treats inside the crate before the barking ever starts.
And you make a game out of going in the crate to get treats / dinner / good things. If your dog gets bones, then make sure your dog gets all bones inside the crate... Bone munching time is a good time to practice shutting the door. You can get two crates and set them up side by side and train both dogs. And maybe put a moving box or large slab of cardboard between so they can't see each other. You can build up to that. I know when my dog is in her crate next to her friend in her crate - both dogs are a lot happier than when they're on their own. Tho it can be hard to get the friend dog out of Frosty's crate sometimes... But you can start with them together and then separate little by little then mix it up so sometimes they're together and sometimes not... But anything would be better than poor dog being shoved in a strange crate in a strange place with no previous experience, no friends and a lot of upset animals.
Susan Garrett has a dvd called "crate games" you can get from Crate Games (Canada) or Susan Garrett's Crate Games (Australian site based in Queensland)
It's probably cheaper to get from Queensland cos the shipping would be cheaper.