I know what you are talking about. When I had my red-tail boa, sometimes the substrate would get stuck to the rat, but it never seemed to be a problem for her, she usually got it out on her own and didn't swallow it. A couple of times I just used the blunt end of a pen to help get it out of her mouth, or off the rat before she swallowed it. To solve this, I began holding the rat by the tail until she took it (they were live). Another option if you don't want to dangle it is to get a pair of tongs and do it that way.