We have an Ifor Williams Pg6, nice little trailer but you can't stand up,in it and you have to crawl in if the pigs won't come out so in that respect bit tricky. We back it up to the gate, use a few huddles to make a pen and feed them by the gate a couple of days beforehand. The greediest pigs are usually the biggest so tend to get to the gate first. On D day open the gate and a few hand full of feed on the trailer side of the gate and shut it quick once the right pigs come through. They tend to be curious to look in the trailer especially if there are some more nuts in sight. On an ideal loading I just use the board to usher them in. On a less than ideal loading it is to stop them doubling back. They definitely sense your nerves and will get agitated when they do so important to be calm. 8 trips so far so not the most experienced by a long way, but it has worked so far.
I cut the feed by half the morning before and give just a hand ful or two at the gate in the evening. Yes it feels mean but I think kinder to the pig than chasing it around the paddock the next day, they need to be hungry enough to go looking for those pig nuts in the trailer.