I actually have done this. It was in my daughter's room, and we had three different wall surfaces when I tore the wallpaper off, so it was either new drywall or this.
It's very easy--if I can do it, anyone can! I just smeared the stuff willy-nilly all over the walls, and when I had a small section (about 4' wide, ceiling to floor) covered, I looked it over and made adjustments to the texture. I didn't get too fussy about it, though, and I think that made it better. It will look different depending on what width putty knife you use. If you're going for the Tuscan look, I'd try to avoid too many curves and use a wider knife. When you're happy with the look, let it dry for a couple of days. Then roll over it with the lighter color. The next day, mix your darker color with the glaze, and take a stack of lint-free rags, and just dip one in the glaze and wipe it over the walls. You'll have to watch for drips, as they can happen several minutes after you've wiped the glaze on, since it gets caught on the texture, then settles enough to drip.
One thing I would recommend is to get a board, probably about 4'x4' and practice--not so much for the technique as to make sure that you like the colors. When I first did this, the room was to be a guest room, and I painted it a sort of barn red, with a darker red glaze, and it was lovely. But when my daughter was born, I wanted to do pink. Unfortunately, I didn't pick the right shades, and it looks too cotton candyish for my taste. I wish I had tested it.
Also, make sure you only mix as much glaze as you need. The first time, I dumped the whole pint of paint into the whole gallon of glaze, and I now have over half a gallon of dark red glaze that I may never use, whereas I would probably be able to make use of plain glaze with some other project. But then, I'm sorta thrifty, so those things bother me!
Good luck with your project!