Oh this is amazingg hairline . Impressive

If you use glue how do you make sure you just apply it right to the start of hairline where the system has to sit?
I ,no matter what I do paste it a bit more or less than the exact hair line . The result , either a tiny part from the front is not glued to the skin or if i have stepped a bit ahead of the line, some shinny glue left. I use my fingers to paste the glue on my scalp.
Do you use any product or anything else to keep the glue to be pasted very accurately ?