If 'bits' are made from non-ferrous metals I clean them up. But mostly they are made of ferrous material and are so badly rusted by now that vigorous cleaning, wire-brushing etc would simply leave you with a handful of red dust....
So I usually just clean them gently with a light brush and maybe some wire-wool, and then treat with a penetrating oil such as 'WD-40' which inhibits further corrosion.