Here's a layout I did using The Photo Project - In An Instant and photos of my "grand dog" Leonard (Leo for short) :
Once my photos and elements were in place, I went to work on the title and journaling. The first step is to choose a font that isn't perfect for chalk writing, because no matter how carefully you write, there will be spots the chalk doesn't cover the board so it's spotty and irregular. I found a few good options (all of which are free for personal use).
2. Choose your font. I liked this one (Film Cryptic) - it's more regular than I could write myself, but it's very readable and still has enough rough edges to be sort of realistic.
3. Once you have your journaling the way you like it, duplicate the layer (I use control + j keyboard shortcut) Set the blending mode of the top layer to "Dissolve." I have to admit I have never used this blending mode before, because it makes everything all spotty and that has never been the look I've been going for before, LOL. I lowered the fill to 87% because it left more bare spots, but feel free to play to see what effect YOU want.
4. Then I lowered the fill on the lower layer of journaling to about half - again, up to you to play with yours for the desired result. To be honest, when I flattened the layout, I lost a lot of the piece-y-ness of the dissolve layer, and so my normal layer was down to about 10%. Make sure you take a look at what happens before you save it or close the file. I should embroider a pillow with the phrase "the Undo button is my friend..." however, embroidery has no undo button and I can only imagine the mess I would make of it.
Hopefully that gives you an idea of some things to try to get the chalky look you want :) As for the fonts, here's where you can download them:
Hope you have fun - I'd love to see how it works for you, so feel free to link me up! (or post on my Facebook page so we can all oooh and ahh!)