I found an amazing, relatively cheap alternative to the new GW crackle paint after doing some research on youtube. It's called Kroma Crackle, and goes for $7.50 for 150ml, based out of Vancouver, BC.
I love the GW stuff, but I have a 2x2 display board I am working on for an upcoming tourney, and I was not willing to shell out hundreds of dollars on who knows how many containers I would need. I apply it over broken up cork board.
The beauty with this stuff is that it dries the exact same, and you can add any colour to it to tint it, as it comes clear. You have to allow a good 2-3 days for a full cure, but man, it looks amazing. I tested it out by mixing in 5% of the GW crackle paint, and it worked out beautifully. The instructions say don't mix more than 5% of the colour you want.
1 tube got me approximately half my board done. Will post pics when it's done.