Start with 220, finish with either 320 or 400, then 0000 steel wool. Wipe a light coat of water on and dry with a heat gun or hot hair dryer; this will bring up the broken wood fiber 'hairs'. Scrape with sharp object or lightly use 400 grit to remove the hairs, then repeat (this is called 'whiskering').
Apply boiled linseed oil by hand as described above. Unboiled, or regular, linseed oil will take several more coats and is more difficult to apply; it will also need refinishing sooner.