Give it a shot (teak oil)! I've experimented quite a bit and found trial and error, mixed with research, to be the best concoction. I have yet to try teak oil so gimme a shout if you do. I don't own a boat, so I'll trade you some catalyzed lacquer for a fishing trip. :cool2:
Typically, if I'm applying a finish while the bowl is on the lathe or by hand-rubbing, I sand to 400, preferably to 600 grit. If I'm spraying something with a cup-gun, I sand to about 240. Also depends on the wood and the intended use.
My suggestion is to turn something out of some cheap--- preferably free-- wood. Check around at local hardwood stores and ask if you can browse their "dunnage"--- wood that's set on the floor to stack pallets of plywood/hardwoon on. These are occasionally 4" hunks of something cheap like poplar. Turn a small bowl out of it, or maybe a spindle if it's too thin. Give the teak oil a shot.
Also note, though, that oil finishes usually don't last that long, whereas the solvent based finishes like polyurathane and lacquer will last a good bit longer.
At Lowes you will likely find Deft clear lacquer. This will do fine. I personally don't use it b/c my cabinet shop is full of catalyzed lacquer, which is light years more durable than cellulose lacquer (which Deft is). It's also free, I get to plunder the leftovers of our paint booth.
Anyhow, just play around. I hit the "jackpot" at certain hardwood stores and I have dunnage, usually 2" square or bigger, made out of jatoba, red & white oak, mahogany, spanish cedar (I have a scraper handle made out of figured spanish cedar, quite sexy), and a few really dark, heavy woods I have yet to identify. Free stuff to play with abounds, just look.