With my new 18 gallon tanks that I've decided to put my vents in, I've decided to silicone the sides black. But I'm having a horrible time getting it on so that light doesn't shine through the sides. I have to keep going over and over the same area. I was using popcicle sticks (clean ones sold for crafts) but ended up just smearing it with my bare fingers with better results. Can anyone shed light on how it might be done more efficiently with less waste? Thanks.