it doesn't matter if it's not sunny outside, it will still do the job

I have put nappies and vests with crazy breastfed poo explosions on them on the line, and they come off it almost good as new. I usually wash nappies in a 60 degree intensive wash, with an extra rinse at the end. 40 degrees is fine if they're coming out clean, but it's better for your washing machine to do hot cycles now and then.
I put cloth pads in with nappies, towels or dark clothes, as long as I remember not to use fabric conditioner!