Thanks Pixie, that has cleared up some confusion - so the ppi will not let me have skinnier brushes.

It seems my brushes and pen nib '1' is anywhere between 2 x 2 and 3 x 3 pixels wide so I think the correct thing to do is go large and then scale it down. Sort of like drawing with a marker pen / sharpie and then reducing it down so it looks like a filigree.

kasey, this type of shading?

section.png