I'd like to recommend regular wet/dry sandpaper for the sanding steps. Sanding sticks are good, but personally I don't use them much. They're expensive and (like most sandpaper) they don't last too long, really. A sheet, 8.5"x11", of wet/dry sandpaper, costs about $0.90 at the local hardware store. Get four sheets (220, 320, 400, and 600 grit) and you're in business. Cut them up into little rectangles and you've got enough sandpaper for several projects.
And to expand on some points in the tutorial:
It's worth emphasizing that using wire cutters instead of actual sprue cutters is generally a bad idea. I have experience with this. The thing is, wire cutters (particularly cheap ones) tend to have dull edges. They work by crushing the malleable metal of the wire. (A sharp edge wouldn't stand up well to metal-cutting tasks anyway - which is why you should never use sprue cutters to cut wire!) Using these kind of cutters on the styrene gates is fairly sure to leave a nasty mark as plastic is torn away. A good pair of sprue cutters will be fairly expensive (around $20-$30) but the thing about 'em is they are sharp enough to cut the sprue very close to the part without damaging it. A really good set of nippers can cut the gate with only minimal risk of leaving a mark.
Personally, I almost always sand down the last bit of the gate that I couldn't get with the nippers. I find I'm a lot more likely to screw up if I finish up with the hobby knife - it's just too easy to cut too far and gouge the part.
Oh, and speaking of hobby knives: fresh, sharp blades are essential. Hobby knives can dull quickly, especially if you routinely misuse them as I do. (For instance, using them as a substitute for a putty knife, or doing a lot of scraping with the blade...) Keep a box of spare blades handy (you can buy a hundred blades for something like $20 at a hardware store) and change them out when they get dull. Dull blades actually increase the risk of cutting yourself, because when the blade is dull you have to apply more force to cut something - which increases your risk of losing control of the blade.
Great tutorial as always...