[Chris Burkard]

Capt. George's advice is sound. If however you want to keep the steps all wood, you can clean, sand and varnish the steps and let them fully dry. Tape off the non-skid pattern you want on the steps (I would allow the non-skid area to go right to the edge of the step), and varnish with (non-skid abrasive added - follow the directions that comes with the abrasive for the best results). Peel off the tape, let cure and you have non-skid without the look of non-skid tape.