I think you have the right idea to try with Minnie again with the kibble gone. Just have to see how it goes. Is Minnie willing to eat canned food? If so, you might have to try a transition to canned, then maybe try some of the things white cat lover has done with Damita (canned/raw 'mix)...I personally haven't succeeded much with that, but to be fair - I haven't tried that hard either.
With 8 cats, it's hard to organize the buffet line here.
To answer your question about the free feed, yes, but - I've been slowly working my way away from free feeding also. I've been upping the canned amount for the ones who don't care for the raw. With the extra canned to eat, they're leaving more and more kibble in the bowl...I just have one pig who's not doing a very good job @ self-regulating his intake
. So we're on to Plan B. I took the kibble up last night to see how it goes.