There are several methods for assistance raising the mast. Most people I know do actually grunt and push it up. However, I use a winch mounted on the mast support on my trailer. I attach the winch to the end of a trapeze wire. After I begin the hoist and get it raised to about my shoulders the helper starts winching. I can dead lift the mast but I have thrown my back out doing so previously.

Another option is to have the boat off the trailer and have an assistant grab one or two trapeze handles. Once you get the mast started, they stand at the front beam between the hulls and help provide lifting assistance by pulling on the trapeze wires. It's very important for them to remain centered with the boat because any side force they give will make the mast want to swing to the side. You can also lower the mast quite easily this way.