Cover your work surface with tarps or newspapers. Use the painters' tape to mask off any areas of the piece you do not wish to gild.
Paint the area to be gilded. Let the paint dry completely.
Paint a coat of gilding size on the area to be gilded. Allow to dry until the size begins to feel sticky.
Place a sheet of gold leaf, gold side down, over the sized area. Rub the back of the sheet firmly everywhere it overlaps the sizing, using the stiff-bristled brush. Gently pull the sheet away. Repeat the gilding process to touch up any large missed areas.
Overlap, for large areas, a new sheet of leaf slightly over the area you've already gilded and repeat the gilding process. Use a soft paintbrush or rag to wipe away any stray gold crumbs. Let dry for four hours.
Paint a coat of clear oil-based varnish over all gilded areas. Let dry and repeat. Let dry thoroughly.