OK so there are a lot of crackle options floating around besides the ready made GW stuff, but its difficult to get hold of down here or it just becomes as expensive as the GW stuff.
I found Jo Sonja's crackle medium (white stuff not the yellow) in spotlight for those down in Aus - $12 for 250ml. So I could do an entire armies with a single bottle for basically the same price as GW little pot.
Soo, this stuff is a medium not a paste, so there are a few tricks to using it. Given this is typically used for large scale arts and crafts ignore most of the stuff on you tube.
sticks to stuff a lot better than GW stuff, so can be dry brushes without flacking.
Cracks really well
takes a long time to dry and does not like to be sped up with a heatgun/hair drier/radiant heater, reverse cycle aircons seems to be ok though.
does not crack as well when mixed with other paints (just paint over it).
Same basic idea as all the other cracking stuff, big crack = use lots, small crack= use little.
How to use it, beside thick/thin layers:
Apply whatever colour you want to appear in the cracks, let it dry. Apply the medium, when its dry (take hoooouuurrs). Assuming your not using it for some ice effects, give it a quick once over with the same base colour and get into the cracks, as the clear layer might cause some oddities within the cracks. Then just dry brush, you can be rather heavy handed.
If you apply a cover to a base all in one go, it will radiate out, so kind of cool if you have something landing on the ground. This is a thin layer, to give you an idea.
You can simply apply it in separate areas, then let it dry and then do another round. This gives a bit more control over where you want big cracks and little cracks to happen on the base and gets you around the radiating issue. Since it actually sticks, you can also imbed stuff in the medium, like the rocks below.
If you go really thick some of the pieces can come off while dry brushing. however, these are easily glued back in place and its been really rare so far. The pieces being thick, tend not to break and since you are painting over it, even cheap nasty super glue that turns white, is not a problem.
I have knocked bases off my table accidently, straight onto a hard floor and it has not broken the crackle, so it does seem to hold up to abuse better than GW.
So what the end up like? 32mm and 40mm bases, painted and 2 layers of dry brushing.