I will try and help a bit
Dry pailing basically means you throw the dirty/wet nappy in a dry bucket with a lid until you wash it. You generally rinse off the excess poo first. I just hold the pooey side of the nappy in front of the flushing water in the loo. It gets the majority off. If there is any major bits left I give it a rinse in the sink before I put it in the bucket.
If there are still marks after the nappies have been washed then just hang them in the sun and it will bleach the stains out for you.
As for how tight they need to be. They need to be comfy, so the elastic around the legs shouldn't cut into the skin and leave welts, but need to be snug enough to stop the nappy from leaking. It is a bit of trial and error, but rest assured you will get told if they are too tight