doing my first brow tint with my new product today as i heard alot of geeks raving about it, i was just wondering what ratio of tint and cream developer i need to put on, how long i need to leave it on, and any tips? i've been doing brow tints for 4 years but have always used salon system, just new to this product. also i am doing an older lady who insists on having brown brows, would you recommend using the light brown or dark brown? how light is the light brown and how dark is the dark brown?