Tape off all hardware and nonwood parts of the cabinet with masking tape.
Sand all the wood surfaces with 220-grit sandpaper by hand, just enough to dull the existing finish.
Use a finishing paintbrush to coat the wood with glaze. Brush it on thickly, making sure to get it into the corners and crevices of the surface.
Let the glaze set for five to 10 minutes. Observe the surface, watching for it to start drying --- the surface will become less shiny. Don't let it dry all the way.
Rub off the glaze with rags when it's just starting to dry. Wipe it lightly, pulling the glaze off the flat spans without digging it out of the corners. Assess the look as you wipe at it, creating the effect you want. You should be left with a partly obscured surface that looks aged and discolored.
Rub a hard, dry scrub brush randomly over part --- but not all --- of the remaining glaze, so it looks as if it's been scuffed and scratched.
Let the glaze set for 12 hours.
Coat the cabinet in polyurethane gloss, using a finishing paintbrush to apply it in a thin, even layer over the whole surface, sealing in the glaze. Let the gloss dry for eight to 10 hours. Sand it lightly with 220-grit sandpaper, and apply a second layer of gloss.