The videos on Youtube make a song-and-dance of it. You just need to proceed cautiously/carefully. I assume you are going to buy some brand of colouring solution in a local pharmacy as you are in a hurry. Mix it as per the instructions on the pack, then mist your system -hair all over with water, ensuring it`s all quite damp [but not dripping water]--simply blot any excess water with a towel. If you have a polystyrene head-form, pin the system to it.
It`s no big deal if you haven`t got one....... wear rubber gloves also. Apply of the solution along the spine of a comb --- again, not too much. Then, slowly back-comb the hair by pushing the comb `into `the hair about 1/2 an inch or so above the lace and move it out to the tips....as long as you apply only moderate amounts onto the comb each time, it shouldn`t run/drip onto the lace ...keep moving the comb away from the lace out to the hair -tips as you move around the various areas of the system... only allow the solution on / in the hair for about 3 or 4 minutes..system hair `takes`colour very fast and can go too deep for what you want in a very short space of time.... rinse the colour out under running water --through the base from the underside so the water runs down the hairs to the tips i.e. away from the lace. Have a look at it when it`s dry and see if it`s the correct `depth`for what you want..if not, re-do it, in the same manner. As long as you don`t dollop the stuff on, it won`t get onto the lace.... you just have to be careful and patient.
Edit: I was looking for that clip posted above [shine-no-more] posted by NYCguy.. I know I have it saved on another browser somewhere....I was typing my reply, while NYCguy was posting his,so we `crossed`--- the clips I was looking at on Youtube were very long-winded..that one above is about the best one around.