The best stuff for liners is called little additions microfleece. Other fleece will work but it is a lot bulkier. Prob is that it is all on clearance ATM so it may have sold out. Go to the counter and ask for the little additions stuff. SL staff are renowned for their black stares and for having no idea of what they have got so if you have trouble and really want some let me know as they still had stacks of it at my local SL. Where are you BTW?

The brushed cotton will be absorbant to an extent but no way near as a cotton terry towelling. Bamboo and hemp will leave it for dead in the absorbancy department too.
Also with the cotton if you make too many layers it will take forever to dry.

If you make some fitted nappies down the track you will be able to use the brushed cotton as the inner or outer layers with a more absorbant panel (such as bamboo) inner layer.

HTH