I use Porter Cable 7424 DA polisher for a few years now. I use Blackfire Products on my vehicles you can get them at www.Autogeek.com I gave up on the color black on vehicles a few years ago. Just to much work. Try putting a paint sealant on that will last longer than wax, then after paint sealant curing time then add some wax on top always seems to give my vehicles a great shine and long lasting wet look !
Back to window leak so the leak is from top rear passenger side or sliding window or both ?