Replying to My composite decking problem HELP HELP!!!

PROBLEM: so i have this composite decking which just plain as shit wont slide, iv made rails with decking before, but i tryed out this new type, its now grooved like the other stuff but totally smooth on top, (which i thought would slide better) doesnt slide for shit, iv even tryed to sand and wax it

QUESTION: so if none of u can figure out how to make the shit slide, i was just gonna suck up the cost and buy some lexan or hdpe to nail on top of the decking, how much would it cost for a 1ft wide, 16ft long piece? which should i choose? should i use coping? recommend a website