Don't ry walking the mast up from the ground, the step up onto the tramp is very awkward.
position your trailer behind the boat with the hitch under the middle of the back beam, this means that the mast can be propped up on the trailer mast support and whilst the base is secured to the ball on the front beam. With the mast a quarter of the way up like this, it is fairly straight foward to stand on the tramp with your back foot on the rear beam and lift the mast upright. [Check shouds are connected first!]