Yes, using a magnetic sail - which is this case is more of a magnetic parachute:

http://en.wikipedia.org/wiki/Magnetic_sail

The easiest way to use it might be to apply it in the direction perpendicular to the dumptruck - Sun axis. That way, you don't pick up radial speed, but you do lose orbital speed.

Assuming, that is, that i've understood how a magnetic sail works.