The thickness dictates the cracks with all the methods and mediums I have used. Right now I also use the brand linked to above (though I had always identified them as Ranger - though looking at the bottle, it says Tim Holtz as well).
In any case, they come in a bunch of different colors and if you don't find a color you need - you can use a light color like the Linen and paint over it any color you want.
http://rangerink.com/?product=tim-holtz%c2%ae-distress-crackle-paint
They also make a crackle clear coat of sorts which you can also use. I think the regular retail price for those is around $4.50 for 1.1 ounces, it is a much better deal than
GWs product (especially when you consider how often craft items like that are on sale for 30-50% off).
Over the years I have used several different versions and methods of doing cracked surfaces (going all the way back to when Dark Sun was first released for D&D). So far, the Ranger product is the one which I am most pleased with. Golden's Crackle Paste - while it gives excellent cracks is a bit fragile on its own and needs to have a secondary varnish applied to strengthen the edges of the cracks and prevent it from flaking off. The Distress Crackle paints though stick quite well on their own and with the color selection - you can fairly well find a color that works and go straight away with it.
I still use two other products for doing crackle finishes in certain circumstances though. On terrain, I will use Modern Masters. They are a crackle finish designed for walls - so you can get them by the pint, quart and gallon. When you want to do a dry lake bed or salt flat board - you do not want to be using 1 ounce bottles.
The other one is Elmers Glue (other PVA glues should work). These are neat, because you can direct the cracks to some extent by varying the thickness of the glue you use - more so than with the crackles paints which are designed to be self leveling. Being able to direct the cracks and how they form lets you finish craters in rock faces with stress fractures that go in the right direction as opposed to any which way.