Like Russ, I was initially a little taken aback when Donnie started talking about painting deck planks. After a little reflection, though, I concluded that it might not be such a bad idea - if done carefully.
Give some thought to how the deck of a sailing ship was built. The planks probably were pine or fir (there were plenty of exceptions), and did indeed turn a dull, greyish color after they'd been stomped upon and exposed to the weather for a while. (Beware of restored ships in this regard; they frequently have distinctly non-authentic finishes applied to them for the sake of durability.) Most basswood has a color (it does vary somewhat) that looks quite a bit like miniaturized, freshly-cut pine. (My own preference for deck planking is holly, but it's hard to find.) But baswood probably is too light and pristine-looking to represent a deck that's been in service for a while. If you apply paint to it like you'd paint a plastic model, you'll cover up the "wood-like" appearance that, presumably, is one reason you're making the model out of wood in the first place. But if you dilute the paint and use it like a stain, to highlight the grain, that probably will work pretty well.
I believe Model Shipways kits come with scribed basswood sheet as a decking material. That stuff isn't bad. You could paint/stain it to taste, then (when it's thoroughly dry) run a pencil or something along the scribed lines to represent the caulking. (Don't, for heaven's sake, use the sort of "wash" technique you'd use to highlight countersunk grooves on a plastic kit. The wash will soak into the wood, and you'll have a mess on your hands.) If, however, you're going to sheath the hull and bulwarks in individual planks (as I gather some participants in this project intend to do), you may want to think about doing the decks the same way. The difference in appearance between the scribed sheets and the individual planks is likely to be pretty obvious - and hokey. Laying a deck from individual planks isn't particularly difficult or, in the case of a small model like this, time-consuming.
For what it's worth, here's how I normally do it. 1 - cut the planks to length. (In the case of the Sultana, this is easy. In a bigger ship you need to be concerned about the locations of butt joints in the deck, but the Sultana is so small that you can assume all the planks of the quarterdeck, for example, ran its full length.) 2 - run a fairly hard pencil around all four edges of each plank. (The graphite from the pencil will represent the caulking.) 3 - lay the planks. Hold them down with Franklin Titebond or Elmer's Carpenter's Glue (my recommendation for virtually all wood-to-wood joints). 4 - sand and/or scrape the surface of the deck smooth. (The manufacturers of those basswood strips do a remarkably precise job, but there will be some slight irregularities in the surface of your deck. Here's where the pencil trick shows its worth. You can sand or scrape that deck from now till doomsday, and the fine, dark grey lines between the planks will still be there.) 5 - apply the stain. My personal preference is the "Driftwood" colored wood stain from Olympic Paints, but I imagine diluted acrylic hobby paint will work. Just don't slather it on so thickly that it soaks through the planks and softens up the glue underneath. 6 - when the deck is dry, give it a thin coat of diluted white shellac. A can of shellac (places like Lowe's and Home Depot carry it) is an excellent investment. While you're at it, pick up a quart of denatured alcohol to thin it. Shellac is wonderful stuff. It's a good, fast-drying gloss finish for ornamental woodwork, and when diluted (about 50%, I'd suggest) and applied to a stain deck it's virtually invisible - but will do a great job of protecting the deck from anything you accidentally spill or smear on it during the rest of the construction job.
That method yields a dull, greyish-cream deck with visible wood grain and realistically thin, dark grey seams between the planks. I don't suggest that this is the only "right" way to make a deck, but I know it works and gives results that, to my eye at least, are quite satisfactory.
On the subject of wood species - don't let the topic intimidate you. Basswood, the preferred wood of American kit manufacturers, is nice stuff; thoroughly adequate for the vast majority of jobs in a model like this. Poplar (no U in the middle of it, incidentally) is a good material for stuff that's going to be painted. It's considerably harder than basswood, holds a nice, sharp edge, and resists denting. Its close grain accepts paint well; cabinetmakers use it a lot. Its biggest drawback is its color, which frequently has a distinctly greenish cast and changes radically over time when exposed to the light. If you get into wood ship modeling deeply you'll eventually want to experiment with some of the more exotic woods - especially maple, cherry, holly, boxwood, and pearwood. But for a 1/64-scale model of the Sultana you'll probably find that basswood will do just about anything you want it to do.
Too long as usual. Hope that helps a little. Good luck.