How dry are they? Sometimes with sugar paste if you fiddle with it whilst it drys you can get really bad cracking, also if it is a bit thick, as the outside dries and then centre stays soft, if you play with it or move it it will crack.
If they are cracking a bit when you are making them you can rub copha/crisco onto to it to stop the cracking. If its just the edges, rub with a damp finger until smooth!
As for the formers, I used aluminum foil for the formers in my boots (see pics). I screw it up and make the shape I need then cover in a smooth piece of foil, then I made the top of boot let it dry, then I made the sole and when it was nearly dry I joined them together. Another way is to cut foam pieces roughly to the size/shape and dry over these.
HTH 
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