I use it for the spots but also in the Walker boom mount and I find it real helpful since sometimes there are large areas that I do and I have to turn around and come back. I really don't like overapplying. I don't mix a hot load but stay in the halfway range anyway. The blue in signal works great and it does disappear with the sun and water. It is not really permanent unless you spill the concentrate and let it sit. Its a matter of preference, it is not very expensive and I am not actually using so much that it is a stark contrast to the untreated spots. I considered a foam marker but the added expense, maintenance and pain it would be for me isn't worth it. Not that it isnt a good idea but I have success with the signal. On top of that I am much more aware of getting "liquid" on my hands with the colorant. Even though I wear gloves and PP gear, I like the idea that if I have blue on me I have poison on me and it makes me safer.