Is the carboy brush safe on the Better Bottle? I was assuming no, and I thought I was told no. I just got a different kind from a different glass-cleaning manufacturer but it seems to be essentially the same material and stiffness. They swear that it will not scratch a plastic carboy. But obviously I am nervous for that to happen. Generally I’m successful just cleaning it by filling with B-Brite or another brewing cleanser, but sometimes that gunk just doesn’t wanna get off. This brush has a softer spongy part at the end which is good, but the bristles still have to enter the neck. Thoughts? Safe or only use on glass?