Josie was probably 8-9 months old when I read the book so we would have started cards around 10-12 months, I think. I went straight to 5x7 index cards, which I file alphabetically in a file box (now two boxes, one for A-P and one for the rest of the alphabet, and did them in basic black Sharpies instead of the big red they suggest when starting out with tiny babies.
I did do a set of red cards (also 5x7 - hey, I'm lazy!
) for Natalie before she became mobile and still spent some time in her bouncy seat w/her reflux, but haven't had them out for ages; she's been using the cards I made for Josie plus words it turns out I never got around to (like "sister!" LOL).
As for phonics, you might want to consider starting there with your older DS; from what I've read, the best window of time for the sight words is until 2-3 years of age, and around age 3 is when the brain starts to "prefer" more of a phonics approach. With Josie, once in a while I'd point out some of the individual letters and their sounds but I didn't make a big deal out of it. Fo example, if I showed her her name, I might point out the J at the beginning and say, "This says,'Josie.' Juh-Juh (pointing at the J) Josie." Then if the same letter showed up in another word I might point it out again. I don't really think I went out of my way to do that, though.
Oh, BTW, in Montessori they do the phonics a bit differently from "traditional" school. Instead of learning letter
names, they learn the
sounds. In other words, instead of spelling the word "cat" "Cee-Ay-Tee" you'd say, "C (hard C or K sound)-A (short A vowel sound) - T (T sound).
HTH!