the key to neat foiling is to place the foils as close to the scalp and as uniformly as you can. If you have a neat pattern of foils you can work your way between them to put the root colour on without too much trouble.
I start at the front and work my way back with the foils and then when i put the root colour on i start at the back and work my way to the front.
Its worked well for me for over 2 years.
Donna