I saw that same blog earlier this year and was excited to try it out.
After extensive searching, I found the flax oil in the refrigerated section of a specialty store...at over $10 for an 8 oz. bottle.
I found the seasoning/coating to be very brittle, and it just doesn't hold up on the bottom of my griddle when cooking bacon on the gas grill. For my other cast iron, it's held up very well on the stovetop. It's fun to play with, but based on $$$ vs. overall satisfaction, I'm still happy with the solid Crisco seasoning method.