You absolutely DO NOT want to put any grease or oil on the L bracket where the bars rest. This defeats the friction that prevents the sway. Clean off the grease on the bars and the L bracket. It should be bare metal against bare metal. Yes, it will make some noise, but just ignore it.
As others have said, Equal-i-zer makes a pad that rest on the L bracket to help reduce the noise and still retain the friction. I purchased them when my system was brand new and those pads are still in good shape. I've not removed them in 2 years now. They do help on the noise.
Any RV dealership that has a parts store should have them, or order on-line. Here's a link to what they look like. I just did a simply Google search and this was the first "hit", so nothing special about this specific business or web site.
Click here. Equal-i-zer Sway Bracket Jackets