My opinion,
Paint the leaves, you already have done the hard work. Rustoeum is a good enamel and let dry for a week or more if possible. I do not believe in liners as they make the spring too thick and destroy the natural damping action of the sliding leaves as designed. There is supposed to be some friction between the leaves. The closest thing you can get to the original special spring grease is the grease packs made for truck fifth wheels. This is almost exactly the same as the original Ford material , graphite filled , very sticky non flowing grease. Do not use chassis or bearing grease as it will just squeeze out and be gone. Get it at big truck dealer parts counter. They are cheap, $0.80 per pack and one will do both springs.
My opinion,
Floyd