Hey there aa0ri,
I had just looked up this same topic and found this post earlier today. Likely the same video that you saw but further down the thread one of our members contacted Lippert via email and they confirmed that lubricating from the outside only was adequate if you couldn't access from inside the coach. I hope this helps!
http://www.thorforums.com/forums/f8/...tion-4561.html
Charlie