I have used a hairbrush in my ex Bhole (she asked me for it), but we used to do anal ocasionally and I would many times insert my finger in her anus to make her cum harder/faster. She was very much into anal, anyway, so using some object there wasn't exactly unusual. I think in this case it was more like she felt like I was the type of guy that wouldn't judge her for putting something on her butt, specially something that isn't even a toy designed for that, so that taboo feel was there and making things hotter for her, for sure. That might be something to consider.
My current girl doesn't cum for the life out of me, but she's not into penetration, so I've tried vibrators with her before, but it was mostly just for her clit. If your girl is really into penetration, you should probably focus on "making your cock do the job". There's many other things you can improve in sex that can make her cum harder or faster, from rhythm to positions that favor her stimuli and the way you dominate her during the act, and bond with her, the psychological part, is a big thing as well.
I would say don't be insecure to try toys, but try improving your penetrative sex as well, you want her to cum hard for your cock.