Disassemble the MDF cabinet doors, taking off the hinges and knobs. Set them on a work space.
Sand the door surfaces with the vibrating sander, just enough to get it dull and flat. Wipe off the dust.
Measure the first span of the first door you want to reface, getting length and width readings. Add an inch to each side -- add 2 inches to total length and 2 inches to total width -- and mark out the measurements on a piece of self-adhesive laminate with a pencil and a carpenter's square.
Cut out the piece using your utility knife, running it alongside the square at the lines.
Peel the wax-paper backing from the back of the laminate piece. Set the piece onto the cabinet surface, letting it overhang all around by an inch.
Wrap your wood block in a dish towel and press it over the laminate surface, scraping it forward from end to end, repeatedly, over the whole surface, to get the laminate firmly secure and free of bubbles.
Trim off the laminate overhang, by running your utility knife along the edge of the door at a diagonal angle.
Repeat the process to reface the front of each door, and the side edges, if desired. Reassemble the doors onto the cabinets.