Hi, I've Purchased Dermélan Pack Online, I've Had Cosmelan Treatment

Hi, I've purchased dermélan pack online, I've had cosmelan treatment 8 months ago and stopped using cosmelan 2 at home 6 weeks ago, can I now apply dermélan mask and can I Di it in 2 steps, cheeks first and a few days later my forehead as doing it all at once was a lot for me to handle