Wrinkles are usually from a cold mold. Did the ones you poured toward the end of your session look better? As was said before, too hot is frosty. A little tin in the lead can make a big difference too, say one part tin to 20 lead. This'd be 1 pound of 50/50 solder to 10 pounds of lead. I also stir in a little lump of bees wax into the hot lead, stir it good, and this'll get much more of the dross out of the lead. Light the wax smoke on fire if you want, so you're not filling the shop up with smoke. If you're breathing smoke though, you need to ventilate better, so you're not breathing in any lead vapor that might be present. I put a cheap bathroom exhaust fan over my lead casting area.
Set the mold on the rim of the lead pot as you're heating it, so it'll heat up too. I always figure on throwing the first few bullets into the remelt pile until my mold comes all the way up to the right temp. Then you may have to fiddle with your proceedure so the mold doesn't get too hot, such as waiting X number of seconds before pouring the next one. I don't care if my sinkers are wrinkly, frosty or whatever, but bullets, or in your case decoy ballast, you'll want perfect casts.
