I recently tried to use the liners on a front spring after disassembling, cleaning and painting it. The liners - on even just a few of the longer leaves - made the spring too thick, so I removed them.
I did grind the ridges off each leaf as well as chamfer each end of the leaves before greasing and reassembling the spring.
The stuff I use is either Teflon or UHMW. Depending on how much the customer wants to spend. Teflon is more expensive but works better.
I usually take 2 of the shorter leaves out to compensate for the liners.
You never grease a spring. Use dry lube, either moly or graphite based.
Springs will last longer if you wrap them with electrical tape or use commercially available covers.