Toppik advice

So my hair loss is very recent and pretty much not noticeable until you actually look closely at my crown under direct light. It's a gift and a curse because I'm not a bald guy yet but at the same time I know it's coming and I sometimes worry if people can see it out in really sunny days or bright lights. I was looking to buying Toppik but I have no experience with it so I was wondering how it should be applied, what I should and should not do when having it on. I also have mostly black hair but in certain lighting it looks a lot more brown so I was wondering, if I get the black color Toppik and I'm out in bright lights would the area I applied to look different or darker than my natural hair which tends to look browner under lights?