A little kief can and does fall off at trim, and you can get kief from fresh trim (by screen sift, bubble ice bags, ect). But it seems to come off wayyyy better from dried (like weeks for leaves) and then frozen stuff.
I like those green plastic lap bins made for trimming that have the screen built in... But it seems youd need to be trimming on the order of many ounces to get any decent kief. Like if you were a pro bud trimmer for hours each day, it'd be perfect. I did buy on of those expensive ass handmade wooden kief shaker boxes, I've shaken ounces through it for hours and barely got anything at all lol! It wasn't for me, now it just sits in the drawer sadly.