Sounds like you are doing well. The key here is that they get used to poo and pee in the bedding, not on towels or other fabric. Eventually you make the bedding section smaller and smaller until it is a litter box.
Girls mark with tiny droplets, hardly noticeable unless you feel it on your skin.
I have four females over a year old and only the last few months are they consistent in pooping in their litter box. Peeing is another story; where ever they feel like it. But during free ranging they are completely house broken as they can come and go in and out their cage.

. In the beginning I had litter boxes on the floor when they were roaming around and gradually took them away until they would go back in their cage to poo or pee.