Keep in mind I'm new to making candles: I'm using 6006, and this is what I do... I leave a little wax in the pan when i pour, When the candles have cooled some and top is firming up, I take my thermometer and poke holes all in the top and make it look awful, then I heat the wax in pan back up and pour it again, (topping off or repour) I guess that's what it's called. Anyway, it usually gives me a nice smooth top without sinkholes. btw, I noticed a lot of times when i grouped my jars together to cool, the sinkholes were worse I think so I don't bother doing that anymore.hth