Dependes what Cracks you mean, for the most part I use Green Stuff for bases, and that\'s only because I have some left over from projects and I always have unpainted minis... (Has anyone every come out even on GS and have ALL their minis painted?)
Sometimes for bases, especially Confrontation the gap on the base is small enough that I use white glue and flock over it.
On gaps in multiple part minis, I use GS too. It\'s especially important on Wolfen to make it look like all their fur is together and it doesn\'t sperate sharply.
Well, once again I\'m not too sure what you mean by cracks, but here\'s what I do.
When it comes to slotta bases I use Milliput (two part epoxy putty). If we\'re talking gaps between the joins on a model, them I\'ll probably use Milliput there again (helps add strength as well!). If I building a plastic kit (vehicles etc) then I have some Italeri mastic putty which is quite handy for quickly filling gaps.
Green stuff,superglue, pins & the power of prayer!
But for bases anything thats on the table at the time. PVA glue, sand, pebbles, sandpaper whatever...
On bases I use greenstuff, \'cuz like Chrispy, I\'ve always got some left over, AND unpainted minis.
For miniatures I use greenstuff to fill joints (like on the old GW warboss model) :] or I use the Testor\'s filler (comes in a grey sqeeze tube). I don\'t like the filler so much \'cuz it\'s hard to get it to look right and takes a while to dry.