Stains in nappy wrap wrinkles

[BumbleBerries]

My reusable nappy wraps have a fleece lined which I understand is pretty standard. They're pocket nappies so the wrap catches the poo and runny poo sometimes reaches the leg elastic, fair enough.

But this stains even if I was it immediately. I know drying in the sun gets poo stains out but where there are wrinkles by the leg elastic the sun isn't going to reach. So how do I get rid of these stains?

I used to get an old toothbrush and would then stretch the elastic out and scrub at the area with a toothbrush and a bit of laundry detergent dissolved in water. Then I’d wash again and they’d usually come out lovely and clean