I found an old bag of Ultracolor Plus and want to use it. According to youtube videos, it's not something for beginners. The last time I played with grout was 15 years ago. So, I am a beginner. I need to regrout a small access panel, and don't need much grout. What ratio of powder to water do I need? Say I use a cup of powder, is 1/4 cup water good enough or too much?