For $15.19, Overton's has a 16-oz spray bottle of Slydz-On-Spray-On Bunk Lubricant.
For about two dollars, there's a large jar of Vaseline in the Family Dollar baby section, and that probably works very good. Just grease the last three feet on both bunks, or something, so's it will slide off the trailer when pushed ..... plus the trailer will totally love it. ....
ha-ha-ha