I have seen people use the master helper, and it seems like a good way to do it easily and safely. The young, strong and tall, can just lift up the mast, but not practical for everybody.
i have also seen people use a long line, attached to the jib halyard. You can have a second person, like your crew, hold the line and slowly raise or lower the mast as you guide it. It seems like at least 50 feet is the right length. The crew takes the line and applies tension way out in front of the boat and trailer.
BTW, always attach the trailer to the car, when raising the mast. If you step Toward the stern, to lift the mast, and the boat tips back, you can lose balance.
Here‘s a thread about the Master Helper: http://www.fssa.com/node/5815