all you need to do is attach the pulley to the anchor, something like a locking biner works well, thread the rope through, and tie the end back to the mast. Gotta pull twice as far but half as hard.
All the drift boat companies sell an "ez pull" system but you can get the couple parts for a fraction at REI or the like. The small climbing pulleys work well and won't rust out.
it looks like this: