Clean surface of tray with a tack cloth. Use painter's tape to mask stripes across the bottom of the tray and up the sides. Yellow and green tape from FrogTape work well on a variety of surfaces, including metal. Press the tape firmly to the surface to ensure paint doesn't seep underneath. This galvanized tray is slightly rough, but if your metal is shiny and smooth, first sand areas to be painted with fine-grit sandpaper and wipe with a tack cloth.