Litter Training help

I have recently neutered my two male rabbits which was 6 weeks ago now. They are separated at the moment but hopefully soon I will try to bond them. Anyways I decided to stop using sawdust in their cages and put litter trays in them. One of the males Lou seems fine using it but sometimes he will tip it upside down in his cage. He uses the litter trays outside of his cage well though.
Lucy (male) on the other hand refuses to use his litter tray in his cage, he just throws it around his cage and pees and poops everywhere. While he's out of his cage he will pee in a litter tray but poop everywhere he will also dig in the outside litter trays and get it everywhere.
Does anyone have any suggestions on how to get stubborn rabbits to be litter trained lol, are there different ways of trying to do it?

Also since I no longer use sawdust what do you suggest I use for the bottom of their cages, I would put a fleece on them but they usually dig on them and pee all over it also with them throwing their litter trays about I don't think it would be wise at the moment.

I use newspaper for my trays and then lots of hay. What sort of trays are you using? I've found large underbed storage boxes work best, harder for them to move, more room in for hay and space to forage round in the hay.

You may find it takes a while before they get out of the marking habit (poos) especially if another rabbit is near. Mine are trained but will still poo where their two areas meet (I have two pairs)

I use these types of litter boxes for their cages, although it says small they can easily fit in them as they are mini lops. My oldest rabbit dash is bigger than them and he can easily use his within his cage.
http://www.wilkinsonplus.com/cat-li...cDPfxIrYzUvEu76RzzM6wutKTeo9AOCB tDs76aYYKg==
I have recently bought a corner one to see if that will help at all aswell.
For when there outside I use these litter trays
http://www.wilkinsonplus.com/cat-li...cDPfxIrYzUvEu76RzzM6wutKTeo9AOCB tDs76aYYKg==

Mine are mini lops too, I still find they need the higher sides of the storage boxes. I use two of these for my lionheads and one similar but slightly bigger one for my lops.

http://www.wilkinsonplus.com/plasti...y8dUIJuQCCx13rdZDgeacKlbIlk7GSB4 v0znqfRbfQ==

Storage boxes, litter trays, corner trays, newspaper+hay or newspaper + megazorb.

Depends how a certain bun is feeling. Just a case of finding what YOUR bun wants.