I have visited Knott's Scary Farm every year for the past 10+ years. In fact, in 2002, 2003, and 2004 I worked in on of the mazes. I've always been a fan of the monster sliders.
In 2008 we decided to ditch the maze and made an open scare zone type area. This resulted in the ability for the monters to move around more and I could slide around. Unfortunately, the driveway is not the slick concrete they use at theme parks.
Being a rougher asphalt surface the plastic knee pads barely slid on it. We tried other alternatives like sheet metal, which did not slide at all, and metal washers, like on the gloves and those came right off. We had to use wheels...
With the wheels, it took no effort to slide down the hill.
How the wheels look when attached and on my knees. Surprisingly, they didn't get in the way much throughout the night.
The wheel assembly we found worked perfectly. It was in the caster section at Home Dept. They cost under 8 dollars each.
They worked great because they didn't require any sort of modification.:
-Rubber coated so it didn't slip on when bolted to the plastic
-A hole in the center.
The knee pads plastic part was velcro'd on. Pulling these off, we drilled a hole to put the bolt through then wrenched down the caster with a washer and locknut.
Mechanics gloves with washers glued on them using a tube of construction glue.
I made metal tips for my shoes using the left over sheet metal from the crappy metal kneepad tests. These worked great as I didn't tear up the tips of my shoes.