1. Protect your work surface with newspapers or an old shower curtain liner. Open the trellis fully. It will be easier to paint the trellis if you can lean it against a porch railing while you work on it. Cover the railing to protect it from paint.
2. Mix 2 parts burnt umber to 1 part ivory black and 1 part yellow ocher on the palette. Thin the paint with linseed oil until it's about the consistency of chocolate sauce -- if it's too thick, the paint will be too opaque, but if it's as thin as the consistency of cream, it will be too translucent and runny. Because the bamboo is smooth, the paint may be somewhat streaky when you apply it, allowing the bamboo to show through.
3. Brush the paint onto the bamboo, covering both sides of the trellis. Keep the brush strokes vertical to simulate the "grain" of the bamboo.
4. Allow the paint to set for a few minutes, then drag a dry brush over the bamboo to remove some of the paint, creating the antiqued effect.
5. Let the paint dry completely (this could take about a week). Seal the surface with clear lacquer or oil-based polyurethane varnish. Mount on the wall with nails.