I did rotate the bottles as I poured the sugar in, but once it was poured in it hardened pretty quickly so that I did not have to keep rotating once it was all poured. I had never done any sugar work at all, so this seemed an pretty easy project for a beginner once the mold was made.
I did have an extra one on hand, but they are pretty sturdy and none of them broke. Of course it certainly would not hurt to have a few extra on hand so you have nothing to worry about
I actually used a Silicone Plastique for mine. It has it's own set of complications though.
I got mine from: www.makeyourownmolds.com
It is a blue putty that you shape around the bottle and it cures in 30 minutes. You have to make it pretty thick so that it will hold it's shape well. I think I used about 1/2lb for one beer bottle. It is really hard to put it on without any bubbles getting trapped. The flaws are not bad and often look like water on the bottle. You have to split the mold up one side to get the bottle out and then hold it together with rubber bands to make more bottles. It comes right out and doesn't stick at all but it is hard to keep the seam from leaking or shifting. Takes practice.
It's not how good you are, but how well you can fix your mistakes.