Yes, I think you're probably right or pretty close. My point is that absolutely no woman, not even Sybil's mother, could break an artist brush, or would even think of such a use for it. Guys, on the other hand, I remember in a book about the Michigan co-ed murders, and have heard regarding misc. other crimes, sometimes use foreign objects. Someone witnessed that two or maybe three white cars were parked down a lane at the edge of some woods, a woman's scream was heard, and a victim was later found to have been raped with part of a tree branch. My son agrees with you. He said that is something a man would do - John grabbed the paintbrush and broke it in half and maybe told Patsy to do something else.
I should pretty much know how women think, since I are one, and since we haven't heard of any female murderers using foreign objects, that Patsy would not even have thought of such a thing. Nor would Luther Stanton have heard a flashlight scraping on the concrete basement floor, nor would the R's have planted a flashlight with no prints on the kitchen counter.
BullMoose has suggested something like a CROWBAR may have been the murder weapon, at another forum, possibly. Works for me, or, even better, a big steel pipe or a shovel. A bat wouldn't have been heavy enough to make that much noise. Neither would a flashlight.