Once inside the box truck, I can turn the bike around using the side stand method and ride it back down. But the truck usually has a 2-3 foot wide ramps, so it's not that difficult.
I've loaded dirt bike onto a pick up, using the skinnier ramps, but again I try to minimize the angle of the ramp by backing the truck into an area that sits up a couple of feet higher than the truck. Using the front brake to hold the bike in position is also a key if you're doing it by yourself so that the bike doesn't begin to roll back down while your trying to get into a new position to complete the loading.
I've loaded dirt bike onto a pick up, using the skinnier ramps, but again I try to minimize the angle of the ramp by backing the truck into an area that sits up a couple of feet higher than the truck. Using the front brake to hold the bike in position is also a key if you're doing it by yourself so that the bike doesn't begin to roll back down while your trying to get into a new position to complete the loading.