Mix three parts shellac with one part lacquer thinner to make a wash coat. If using wood dye, choose a color that complements the natural tone of the wood.
You can mix same-brand dyes together or dilute the dye with lacquer thinner to achieve the desired tone.
Transfer the wash coat or dye to a spray can. Spray a light, even coat of the product over the entire poplar surface to seal the pores and, in the case of dye, establish an even base color.
Allow the product to dry before proceeding.
Sand the surface of the poplar with 220-grit sandpaper, sanding with the grain.
Dilute one part stain with 12 parts lacquer thinner. Spray the mixture evenly over the poplar's surface and wipe away excess, wiping across the grain first, then with the grain.
Wait for the stain to dry, then apply additional coats the same way until your poplar is the desired tone.
Apply a wiping varnish over the poplar's surface with a rag, wiping across the grain, then with the grain. The varnish will seal and protect the stain.