I used to move 600 colonies onto apples each May. We loaded them one at
a time by hand. The only time there was trouble was when we screened
them in. They seem to get panicked when screened. Moving unscreened bees
is really no big deal. Two people on the ground smoke the hive, and load
it on the trailer. A third person on the trailer smokes it again and
moves it into position.The bees hardly come out intil the hive is into
position. Place the first row with the entrance facing back, and the
next row facing forward. Because of the protruding bottom boards, a 4 -
6 inch channel is created. Repeat the pattern till the trailer is
loaded. When the destination is reached, blow lots of smoke into the
channels from the upwind side. The bees will go back in the hive.Pick
the hive up and unload it. I've done this without veil or gloves many
times.In really hot weather, increase the size of the channels between
hives with a 2x4 laid flat on the bed.
    My bees are on pallets now. Palleted bees don't even need to be
smoked. Sure they come pouring out, but if it is dark, they don't leave
the outside of the hive. I would think moving bees permanently located
on a trailer woul be done similarly. Wait till dark, hook up the
trailer, and go.