If you think it is going to be difficult I would pop the trailer in place a day before so they get used to seeing it. Try and create a funnel at the entrance to your pen, tin is great, if you can whack it into the mud even better. We keep off feeding them, make sure they are proper hungry then load, shaking the nuts around. Put straw on the ramp and in trailer.
We have learnt not to put any nuts on the ramp otherwise the pigs stick on the ramp and don't like to get further, we take our time and make sure we have enough time and .......lastly but most importanty, don't force the pigs into doing anything. One thing you can be sure, pigs are stubborn and if they don't want to do anything, they wont.