Anyone w/ cats & ferrets? help w/ poo

My new kitten is pooping where the ferts poop. Since ferts poop so much I just have newspaper in every open corner. I had 2 litter boxes in the house before the kitten came & since then I got (2 weeks ago) I added 2 more litter boxes to the house. I can not afford litter boxes & litter for every corner in my house & the cats poop & pee is much bigger than the ferts so the paper soaks it up so quickly & makes a mess. Uggg I thought the poop was bad before LOL

Does anyone know how to deal w/ this. The major problem is that I can not catch her in the act. I have been trying for 2 weeks to train her to go in the boxes. I do move her poops from the paper & put them in the boxes & I keep putting her in the boxes when I think she may have to go & I reward her when I see her going in the boxes. I also keep them clean (but sometimes just leave one terd in there so whe knows where to go) but they are not working.
I know she knows that the boxes are the right place to go but the ferts are training her to be a fuzz-butt. Darn those weasels LOLLOL