I've actually tried this 3 times:
1st time I was super horny and tried inserting a small toothbrush handle, because it was my first time. It went in easily and i came, but i didnt notice any difference.
2nd time was a few years later, i tried using an even smaller toothbrush handle and came instantly! But that was because i had been masturbating for 1h before that
3rd time i tried using my finger, but didnt wash my asshole beforehand, so when i looked at my finger, it was all crown, and it turned me off...