BUT in the meantime I spoke with the casters and they seem to feel it's the Smooth On 305 that's the likely culprit.
I have a couple of castings that are prototype-worthy to add final details to. But I'm going to see if they can get a cleaner one for me. For the cost of the USPS flat rate box... and a few bucks to them for resin, it's worth it for me not to waste a day playing around with bubbles if they can get a better one. The mold is pretty nice and while I've been beating on em with casting after casting - and a bit or two torn off from mane undercuts... yet I think they've got lots of life left.. ;)
I have a MOST awesome bunch of tips coming up about pin-holes and bubbles next though. Gotta recharge camera batteries. These are just too perfect as examples not to use to share the info. Trots off to bed now & to pop the batteries in the recharger. ;)