When we did repair work on the Smart & Brown model A at the museum, I made a new leadscrew nut out of gunmetal, and to keep most of the swarf away, I bought some telescopic tubular springs to cover the leadscrew. I'm glad I did as the leadscrew always looks like it has just been washed. You just pull back the spring each side of the apron and squirt oil over it every six months.
They are available on that website we are not allowed to mention, so no helpful links from me anymore.