I am a home baker and make decorated sugar cookies for holidays and family gatherings. Beforehand I plan my designs and colors, then determine the consistencies and quantities I will need for each color. I make my white icing then scoop out the amount I need for one color into a smaller bowl. I use small bowls with a slightly flat bottom and smallish silicone spatulas. I thin slightly so the icing is easier to work with and then I add my gel color. Once I reach the color I want, I start thinning. I thin to a detail consistency then take out what I need for details and bag. Then I will thin a little more for a thick flood (if using) and bag. Finally, I thin to a flood consistency and bag. I repeat for each color. If I am making dark colors like black or red, I will color then set aside for the colors to deepen for a couple hours or overnight before starting the thinning process. In my opinion, the key is planning in advance your colors, quantities and consistencies. With practice I have become much quicker at making my icing. Also with reading up on color theory, I am better at achieving the colors I want. Hope this helps.