On a trip this past week I had a container of silicone grease open in my Northface backpack (brand new, first time using it). Luckily it was in the top flap pocket so only the flap and 2 items (clothes) were affected. I tried a few different ways to get it of while on the road (lemon juice, hot water, I rubbed off as much as I could with a cloth), but there is still a lot on the items (at least they are really waterproof now). Any ideas how I can get this stuff off? Thanks in advance.