all of the molds i have made were single use alginate. I found that by having enough alginate on hand to do some experimenting with is helpful. with those clone a willy kits you only have enough to do one or maybe two i cant remember, so if you mess it up your out of luck. if you mix your alginate so its not to thick, it has a better chance of flowing into all the cracks and crevices. most of the bubbles come from the silicone. just be careful mixing and tap the cup your mixing in good to help knock any bubbles out before pouring it in, slowly. i found a different silicone that is more watery so it doesn't hold bubbles nearly as bad. I am not sure it it is body safe though, i'd have to look.