I've painted with tincture describing a 2-inch patch on different parts of my body. For the inner arm, it took 2 hours to absorb. For the bottoms of my feet, it took a little over three.
Absolutely, do not drink tincture! It's fine for painting, as far as I've read, but internally, nopers. And, I wouldn't waste Lugol's on painting - that stuff's just too expensive!