I don't know if anyone has already discovered this... but here you go.

For a better hold and a clean front... I apply Ultrahold, not too little, not too much...

Then... here comes the trick:

I comb over the glue with the tip of the glue to:
1. remove excess glue
2. spread the glue evenly
3. form a grid in the glue

it should offer a cleaner and stronger bond with the grid trick. i discovered this on my own while experimenting in my search of a perfect hairline.

Hope it helps.