Just make sure to use a good sharp scissors..preferably new... part the hair either side of the `cut`line so as to avoid cutting across the hairs i.e. just keep the hairs out of the path of the blades....you could also pin the system to a styrofoam head and that will hold it and `free up`your hands so you can easily part the hair and cut across the lace using a hobby-knife such as one like this http://www.draftingsteals.com/xacbranknif.html
If you intend bleaching knots [ you shouldn`t really need to at the front especially as the factory does them] you`d have to do it before sealing knots with knot -sealer, which is an acrylic coating....that would prevent your bleaching solution from getting at the knots...so don`t put the cart before the horse ! Hope it goes fine /works out like you want it. Paul.