For hair, that is.
My hair is now a tad over chin length, razor-cut into a few long layers. I’m too lazy to waste my time blow-drying it to turn UNDER at the ends. It has developed minor waves IN THE WRONG PLACES and the waves aren’t symmetrical, to boot. The waves are more like ornery cowlicks in dumb places.
Would a wet-to-dry flat iron straighten out my hair?
I also have a full set of hot rollers which I think are (again) a total waste of time. Ditto a “brush roller” thingy that hot air blows through.
I want volume +body + straight. What to do??? 
I have a wet-to-dry flat iron, but don’t really like to use it on fresh-from-the shower hair. It takes a long time to get it dry that way. I use a blow dryer and a vented paddle brush (medium-length shag cut, the back just brushing past shoulders and front just at shoulders, bangs with a cowlick on the left). I dry my bangs all the way dry because of the cowlick, and the rest just so it’s not sticking out, but the paddle brush is imperative or it would all be sticking out.
The flat iron, I use on off days, and will mist my bangs with water and then use the iron to straighten the cowlick out. The rest I use it dry just to slightly curl under anything that went crazy while I was sleeping. I love the flat iron, and tossed my old curling iron. The flat iron is also useful for ironing pant cuffs into place and for wrinkly upturned flap pockets!
I think it will still be faster for you to blow dry first. With your length hair, I can’t imagine it taking more than a few minutes. Then use the iron to straighten out whatever’s still unruly. I find that just doing the blow dry straightens out more than you would think, and mine’s a lot more wavy and has less body if I let it air dry.
I have this flat iron, this vented brush for blow drying, and a blow dryer similar to this. Plus a couple of combs, that’s all I use.
I use a wet-to-dry flat iron, I love it. I agree it doesn’t work well on wet out of the shower hair … I usually let mine air dry to the point where it is damp, but not wet, and the flat iron works just fine then. It takes about the same amount of time as blow drying and then straightening, the difference being that I can do other things while it is air drying.
When you get used to flat ironing your hair, you can create a little kick at the ends, but it’s not the same defined curl as using an iron or hot rollers or even blow drying on a round brush. If you just want just a little turn, you’d be okay with the flat iron, but probably not if you want more bounce.
Volume, I don’t know. It depends on your hair. Straightening it will make it sleeker, and hang better, which might give it more of the look you want. I use a little product to gain some volume, a leave in conditioner and a spray to get rid of frizz. If I apply the stuff too heavily, it can make my hair look lank, so you may have to play around to figure out how much to use to get the desired effect.