You just found out one of the downsides to the silicone background cover method. If you don't get complete coverage the first time around, that is what you end up with. You cannot touch it up like other methods because silicone will stick to almost everything in the world EXCEPT silicone. That is why I use brown silicone for the rare times I use it, but otherwise I use titebond iii wood glue and coco fiber to cover all my backgrounds. You can do multiple coats if needed, no fumes and no need for gloves, unless you want to use them. Although, it does take twice or three times longer to dry and cure. The other advantage is that you don't need the cocofiber to be dry before using it.