Itll be a ton easier when they are spayed/neutered. Baby and teenager bunnies like to leave poop everywhere because it helps them claim some territories. Some buns leave little accidental poops if theyre too happy and hyper to run to the litter box, too
My trio was pretty easily litter trained. If they leaned back to pee, my boyfriend or i would rush them over to the litter box to go. If they left poops outside of the litter box, we would throw it into the litter box. If we caught them going in the litter box, they got a small bit of a treat. And of course, some (most?) rabbits like to poop close to where they eat, so we layered their litter with hay. They eat one side and do their business on the other side
It took maybe 2 months to have all three fully potty trained. But all of that flew out the window when our little Badger hit puberty. The other two still use the litter boxes, but Badger goes anywhere and everywhere. This will stop when hes neutered