I just did mine today and I also have a 07 Classic. Its really hard to see in the cells of the trolling motor batteries as you probably found. I rigged a small piece of broken mirror on a strong good size clamp like you would use to hold something together when gluing. That and my really nice and bright small BCB flash light allows you to see in each cell to check water level. From there use a turkey baster or what every you can find to add distilled water to cells.