I do all mast raising and lowering when the boat is on the trailer. That way you can leave the spipole, halyards, shrouds, trapwires, etc attached which saves a lot of time setting up. (And because I'm lazy!
)
A couple of weeks ago I fitted a small $30 winch to the front trailer mast support, all I have to do now is:
-Attach the mast base to the front beam/ball.
-Lay the mast at an horizontal angle so that one of the shrouds is slightly tensioned (This is to prevent it swaying sideways).
-Attach the wire from the winch to a trapeze wire.
-Winch away as fast as you can
The same thing goes for lowering, but at some point the pulling angle becomes to steep so you really want someone to help you with that. Also I will replace the winch-rope I use now with steel cable or dyneema for its strength and non-stretch properties.
I'm surprised so little people use winches since they're so easy for pulling your boat on the trailer, etc.